I have problems with 't' char on my keyboard, so this is the reason why I found this bug.
So, when I try to stash files by staging them, selecting *all of them* and selecting Repository -> Stash Changes... in the menu, I get dialog box "Stash Changes?". then I start typing a message and find quite often that my 't' chars are missing due to keyboard problems. then I switch to another application and copy 't' character from a text there, then I return to Sourcetree.
As soon as I return to Sourcetree, the list of staged files is updated/refreshed and only first item in it, keeps selected. At this time "Stash Changes?" dialog box is still on top and nobody notices that in the background, the selection has disappeared from almost all files. I choose "Staged files / Selected files" and click Ok. Even though all files get stashed only one file disappears from staged ones (the one that was selected) and the rest are still there.
Win10, Sourceree 3.4.25