I've hit an interesting problem with backing up my attachment files. Turns out that while macOS and apparently Zotero count the length of the name according to display characters, iDrive is counting bytes. So certain names are too long for them to back up (255-char limit?) as they read them longer than the Zotero does. Greek characters cause this problem for me.

I'm not quite how to solve this other than shortening the filenames (I use 100 char of the title) or having Zotero do it for me behind the scenes, which may be a bit of an ask.