I am not exactly sure how to reproduce this but it happens consistently. I think a way to reproduce this is to have a list of stashes, click on the last one, right click and delete it, confirm, then the UI takes you back to the file status. Clicking on the new last stash does not update to it. I'm attaching a screenshot showing the end state, where a stash is selected but the file status is still being displayed.

BTW, this bug has been present in Sourcetree for years. I am not sure how it has not been reported (maybe it has but I'm not sure how to search for it) or fixed, as it is quite obvious to anyone who uses it for any length of time.

Update: it looks like I don't have permission to attach files. :/

Update 2: I am using the latest version 4.2.14 but the version dropdown does not list that as a choice. The latest released version it lists is 4.2.11, with 4.2.10 and 4.2.12 being listed as unreleased versions.