Hi Nya, thanks for mentioning this. Today I was working on another part of the app and noticed that the way we manage the path to the download folder could become "stale" (file/folder bookmarks).
One possible temporary solution, as you mentioned could be to change the downloads folder to something, then back to a destination under "On your iPhone/iPad".
Please let me know if this fixes for you all that have trouble with extensions, this could help put me on track to a fix.
Thank you all for your help!