I've been having some issues with the "Refine Edges" tool when it comes to selections. After carefully selecting my subject in the picture, I intended to refine my selection when I noticed that as soon as I clicked on the "Refine..." button, the edges of my selection became fuzzy and inaccurate right away, making my overall selection much worse. This happened without even altering the settings or painting with the brush. After spending plenty of time trying to refine the selection with the help of the "foreground" and "background" brushes the result was not much improved, so I had to resort to Photoshop in order to get the job done.
Here you can clearly see the what happens:
Now I'm aware of the low contrast in some of the edges which make the task more complicated, something moderators keep mentioning in similar posts forgetting that's often the case in real-life scenarios. However when I managed to get a nearly perfect selection on Photoshop, I realised that was just an excuse (not to mention the improvement "Decontaminate colors" makes, a feature currently lacking in Affinity Photo).
You can find the original image and my results in Photoshop as a comparison below, as well as the .afphoto file with the original selection saved as a Spare Channel, in case you want to give it a try. I've seen several posts regarding this issue, but since no actual solutions where provided and the topics were just forgotten (as you can see here, here and here), I decided to post about it myself before having to unfortunately switch back to Photoshop for good.