Screenshots keep coming back after cleared, how to delete permanently?

I use both Brave and Firefox to run some macros in local storage mode that capture screenshots among other things, then export them. Eventually the screenshots add up to hundreds or even thousands of files, and although I hit “clear” in Ui.Vision and they seem to disappear in the window, the next time I load it, they are back again. I also tried doing a backup, deleting them from the backup, and then restoring the backup to see if that would take care of it, but that has no effect, either. How do I get Ui.Vision to actually delete the unnecessary screenshots?