Selection Brush not snapping to edges

[PaulWall]

I am struggling with the following action and would appreciate any guidance.

I am fairly new to Affinity and the steps i have taken very  carefully follow tutorials i have watched on U-Tube where but i don not get the same results. So I am not sure if i am simply doing something wrong or i have some sort of technical issue as explained below:

I am trying to select a persons portrait to isolate them from the background. However when i use the selection brush, freehand, polygon, snap to edges, the 'marching ants' only snap to the edge when i am running along the edge of the photo. The rest simply stay in the drawn position and do not move at all. 

If I then follow up with the Refine option, be it using the Matte, Foreground or Background options, the selection simply copies the area marked by the brush and makes no attempt to refine the selection. E.g. if i select Foreground, and paint along the required edge, the whole 'painted' section becomes the foreground, with no refinement of the edge selection at all. I have tried varying the brush size with the same results.

The photo was originally a RAW file which i simply opened and Developed within Affinity for further processing in the Photo persona where I am trying to do the said selection on a pixel layer.

I am using Windows 10 on a laptop, with Affinity 2.2.1.

[v_kyr]

Hard to tell without seeing some screencast here of your attempt on a portrait and the snapping and selection brush settings. - Did you already looked at this tutorial here ?

Further it's also possible that there are some bugs related to this in APh 2.2.1.