On up-to-date tests-passed.
I tried to approve a new user today which popped up as notification needing approval, but when I navigated to the review queue I was presented with an older approval I’d already actioned and upon trying to delete that user again (it was a spammer) it appears I’d deleted the new user. The record I’d been shown visually was not the same record the system then deleted. Most odd!
So tried this again (after the user kindly re-applied) and the same issue happened, but as workaround I looked into Admin -> Users -> New and approved the user’s record manually without using the review queue UX
Apologies for lack of extra information but just suggest this might be one to look out for, very confusing and I ended up blocking the wrong user …