Jaimoe

Indeed, it doesn't look good in general sense way, somewhat sloppy thought its actually trivial and non-important once being revealed.
It is certainly something that affects how general public looks at Affinity Photo, I myself am glad that more important functions don't fail, and that this forum can provide solutions to the ongoing problems.

Hi, yep, as mentioned, with looking at some other posts and more observing, I've found out the issue is just about deceptive progress bar, which stays at zero until export is almost finished.
With enough patience all exports were completed.
I have utterly miserable PC configuration, so I can hardly say it's software fault that I have to wait for extended period of time. AP is actually very quick on my inferior machine compared to all other software I use. The reason for posting is that previous exports were indeed much quicker, but now after enough files processed I can say it's directly related to number of operations within files. When I have lot of layers, it is always slow.

Thank you for trying to answer. It took me time to read this article, yet I'm trying to understand what is "contribution" in Affinity Photo, how it differs from plain measure of amount, controlled by the other slider.

Hi, I tried to find it by moving there and back, but couldn't: contribution slider on denoise filter is a mistery to me, how does it differs from amount slider? 
It looks to me that both sliders just affect the amount applied, be it luminance of colour denoise.

(My apologies if this same procedure has been posted previously.)
Suppose you have two adjustment/filter layers called "SourceLayer" and "DestinationLayer".
Suppose you've created a mask on SourceLayer, so that it affects only part of your image.
Suppose you want DestinationLayer to affect only that same part of your image.
 
1. Select SourceLayer.
2. On the Channels tab, right-click SourceLayer Alpha.
3. Choose Create Spare Channel from the menu.
4. [Optional] Rename "Spare Channel" to "SourceLayer Mask".
5. Select DestinationLayer.
6. On the Channels tab, right-click the icon of SourceLayer Mask.*
7. Choose Load to DestinationLayer Alpha from the menu.
 
DestinationLayer will now affect the same part of your image as SourceLayer.
*If you don't click the icon, you won't see the "Load to..." menu selection. This is a (minor) bug in Affinity Photo.

Hi Jaimoe,
Welcome to the forums
Does pressing Q to quick mask do what you are looking for?
Thanks
C