At the moment, the default settings for screenshots is "keep for 3 days". Sometimes, an installation/update can revert the settings to the default, which will automatically delete all screenshots older than 3 days. For me, it deleted over a year's worth of screenshot data as a result of an update. Fortunatelly, not all was lost as I had a backup of some of the data.

The system should include a test that if it needs to delete an unexpectedly large number of screenshots, it warns you in advance. The prompt could be something like "Manictime will delete X as a result of a change in settings. Would you like to proceed" (where X could be the number of folders (i.e days) to be deleted, or the number of screenshots, or just the text "a large number of screenshots") with the buttons being "Proceed" (in which case the files are deleted) and "Change Settings" (in which case, the files remain, and you are taken to the settings menu to adjust the screenshot settings).

In normal practice, when the system is just deleting the expected number of screenshots as a result of the reaching the days/size limit under the current settings, this pop-up message would never appear.