ARTGIRLJENNL

@SrPx @ARTGIRLJENNL
Hey folks. I have confirmed that this is a logged issue with someone on the development team. They were able to recreate the issue on their end and confirm that it is indeed a bug specific to Affinity and not influenced by settings outside of the app.

The more you zoom out, the bigger and more jagged and jittery the selections become, and only when using a drawing tablet on desktop (for some reason this issue doesn't happen with a mouse) and/or Apple Pencil on iPad. It's almost like something in the coding is affecting the stylus accuracy, and is causing this look where it seems that the cursor is snapping to an invisible 90 and 45 degree grid. I've found that it also impacts the brushes, making them feel a bit more jittery and sensitive to pressure input,

In the meantime, as a temporary fix, install this app: http://hejstylus.com
Hej Stylus is a third party brush/cursor smoothing app. The basic version is free, and you can just use it with the 'Position Pull' at its minimum setting - that's all you need, unless you plan to use the more premium features.
The Windows equivalent of this app would be Lazy Nezumi: https://lazynezumi.com
These apps somehow override the stylus input and makes it normal again - and it makes the brushes feel a lot more like PS brushes too (I suspect that the same issue with the Freehand Selection Tool affects the brushes as well since it's all linked to the stylus input at the end of the day). It's not a perfect solution, but it's an 'okay' workaround until the issue is addressed in the apps.

Since they are aware of this, I hope we can see a fix in the near future - fingers crossed to see a fix in the next update!
I use the freehand selection tool religiously in my work, so this bug is causing all kinds of havoc. 

Wow. This is big.... Is (should be...) a priority as is about selections minimum quality... is not any more a painting specific feature. Selections (and masks) are the absolute base of all in photo retouch and image editing in general.... So, fixing that issue seems would both fix that problem with the brush (and some others), and the selections (and surely other matters).
Well, definitely, I hope it get fixed.
I knew the two (external stabilizers). Obviously never used hejstylus as I'm in Windows since always (she is, too).  I believe there is no free version of Lazy Nezumi, but is too long ago since I tested it.. In my tests internal stabilizers work a bit better than Nezumi (ie, Krita, PS or Clip Studio's). But it indeed can be set to something one can work with after quite some fiddling. While I was having not (or noticing) issues in Photo, since long I mostly paint and draw with Clip Studio, and then export and import into Photo, and do any image editing operation there. Most of the times is for preparing the PDF/X for print, etc. But would love to make Photo my painting tool. It has all the features I as an illustrator, comic artist and etc would need. Is just these fixes in the brush system and related matters what are needed.
Could this bug (or bugs) be related to the matter of producing jagged lines just like these, as in a grid (since long I had been thinking is kind of a mismatch in resolution, and that it uses suddenly a coarser grid or something) when one zooms out, a lot and draw/paint ? (as you have exposed, it's happening with selections, but obviously is related to the cords system or something, and related to the tablet. Because for quite some time, if you want to do a fast sketch, or even final inking work, line art,  in an A4 at 300 dpi, fitting in zoom the canvas to the Photo work space (at a 16% or whatever the zoom is that), it will produce the lines to go vertical and horizontal zig-zag in the lines, producing a stepped jittery line, as if following a coarser grid. This typically was avoided just by using the "smoothing" feature (the stabilizer) in Photo , doing so with my machine and tablet, it eliminated the "grid" irregularities, and allowed producing good lines when zoomed out.. Unless some recent update has changed this behavior... (I'm not checking the betas lately, only the stable releases). 
Native stabilizers I think work better, and these two apps make the thing a bit cumbersome in your everyday workflow ( they are fantastic, anyway)
PS: Nezumi or the other could by a temp solution for some, not for others, but is something.
 
 

@SrPx
Yeah, it's super big - having perfect selection tools and tablet input should be a huge priority for any art and design app.

I would say that a majority of Affinity users use tablets at some point or another, and just about everyone will need to use the Freehand Selection Tool and brushes for various tasks. I've tested out Photoshop, Clip Studio Paint, Sketchbook Pro, Krita, ArtStudio Pro, Medibang Paint, and more, and Affinity is the only software that does this. It's definitely linked to the way that the apps interpret the input from the stylus/pen. I use Affinity Photo as my primary painting/illustrating tool, but I'm forced to resort to workarounds (which can sometimes hinder productivity and can be very tedious) until the issue is resolved. When this issue is fixed I'm sure that a lot more people will love Affinity, because it will have a massive positive impact on a lot of the tools within the apps for any user who has a drawing tablet. I haven't found that using the internal app stabilising features help, unless you have them set at a very high number, but then drawing becomes very difficult and unnatural. In addition, there's no stabilising feature when using the Freehand Selection tool anyway, only for the brushes and eraser.

Like I said, the people over at Serif are aware of the issue, so hopefully they can find a fix for this issue ASAP.

Have just tried fiddling with the the projection, no change. Weird thing is when selecting from the toolbars the calibration is dead-on with the pen, when moving to the work area it moves way off to the right. Frustrating for sure!

I am using a Huion Kamvas Pro 13. Have tried with Windows Ink activate and then again with it deactivated. The issue still remains.

I am having the very same issue PLUS this additional one....not only are my lines ragged when using the lasso tool with my pen tablet, when turning the preferences on as shown below, my calibration is thrown totally off for my stylus. As soon as I uncheck the 'high precision tablet input' box, the calibration is corrected.
Like the OP, I am an illustrator and used the lasso tool in Photoshop in creating my artwork to create fluid shapes, fill and mask. Now the edges are so horribly choppy that I am needing to go back to my old Photoshop program to create in as these irregular lines will never fly with my clients and frankly, I wouldn't accept the work in this state either.

I've attached a screenshot for you to see the choppy edges...
 

@SrPx
Thanks for explaining! 
Unfortunately this is not a Yiynova issue, but could very well be related to the way that Affinity registers input from a drawing tablet in general - I've had the same results with the Yiynova, a Wacom Cintiq 13HD, Wacom Intuos Pro, on my desktop computer and laptop, and even noticed this at times while using Designer/Photo on iPad with an Apple Pencil. 
Selections in Photoshop (and Clip Studio Paint, Sketchbook Pro, ArtStudio Pro, etc) are perfectly smooth and clean when using the Yiynova, so this is definitely an issue with Affinity apps themselves. Chris B, a moderator, has even confirmed this (above). 

You are correct, at least almost correct. I'm not a comic book artist, but an illustrator that uses similar techniques. Flatting isn't really an issue as the flats go under the linework, so any misaligned/jagged selections are usually covered by that. It does show a lot when doing more refined selections for colouring though, such as a cut-and-grad shading/highlight technique. The edges of the highlighted areas are a bit 'wonky', and it shows in the final work. For the moment I'm using the quick mask feature in Photo to create selections using the brush, but it's a bit more tedious working in this way. 

Unfortunately I'm working on an iMac, so I obviously don't have Windows Ink. I can't seem to find the "High Tablet Precision" option in my Affinity Preferences - where is this? Is it only in the beta perhaps, or maybe only for Windows machines?

I can definitely provide a video/screen recording of the if @Chris B thinks it would help with finding out what the issue is (just let me know Chris).

I just want to let you know this is logged but it hasn't had a response yet. I believe I saw another post similar to this which reminded me to let you know. 

Hoping to see a new and improved brush management set in the next big release of Designer.  I've used Illustrator for more years than I care to admit and have always found it useful to be able to easily pick up attributes from one line (or object) and apply it to another.  And to see what brush I used in the first place.   

This might be a silly question, but is there a way to find out which brush was used for a particular line? Just selecting the curve's layer doesn't seem to cause the brush that was used to be automatically selected in the brush panel and with both "the box set" and "Daub Essentials" I've already got quite a few brushes and it's hard to remember which was used where.

Hi. 
I often design seamless patterns and would like a way to test if I did it correct. In illustrator I tested this by fill a large square with my pattern.

Is an option to import custom shapes from Photoshop  (*.csh)  in a shape library of Affinity also somewhere in the roadmap?
Thank you.

I think I may have mentioned this before without getting any feedback, but I would really like to have a tab/place to save symbol/shapes we create. A lot of software programs have Shape Libraries where they can save and categorize shapes. This makes it so easy to grab a shape and insert into the picture and save a shape we created while drawing a picture.

Hi,
What you quoted is a Macro not a video, (aka an Action in Photoshop) and needs installing into Affinity Photo to utilise.