This is what a psd file looks after saving it from Krita (2.9.10). As you can see there are some strange colours in the thumbnails. There are also two different files saved. One has the proper file name, the other a ~ (tilde) mark behind the .psd (*.psd~). The sizes are different as you can see, but not the images when I open them in Photoshop or any other software.

This way I have to open all psd files in Photoshop, resave them to get the proper thumbnail, and then remove the *.psd~file...

I have reported in this issue before I think...

Henry