Please help: Paint bucket and selection tools always leave 1 pixel edge / Painter 2020

Dear Painter Community,

I trying for weeks to find a solution for my issue. I'm would very grateful for help, because I cannot find any solution for this problem in the painter manual nor in this forum or somewhere else in the internet. :-(

If I'm selecting an area with a selection tool or the magic wand and then fill it with the bucket tool or delete the selected area it always leaves an edge of appr. 1 pixel. I always have to expand my selection manually via the selection tool settings that this is not happening but then ist not 100% accurat. It looks like that it only filles or deletes whats inside the selection but not the line of the selection as well. 

This bothers me for a long time now. I'm a newby to painter and i'm using painter 2020 (bought version) but I had the same problem in painter 2021 (cloud version). In photoshop I was able to change the presets of the selection tool so that it expands the selection permanenty to the pixel I have set and I don't had to expand it every time like I have to do in painter right now. 

One he following pics you can see what I mean. I created this form and then selected it with the magic wand. After I deleted the selection the edge of the selection is still there (second pic). Same thing happens when I use the lasso tool or the paint bucket. :-(

Can anybody help me with this problem? 

Thank you for your help in advance!

BR Silke