Files dissapear during synchronisation or copy from another date

Hey all,

I have a problem with my files during synchronisation or when i copy the lesson plan including files from another date or class. 
It happend to me quite often, that during one of the above mentioned actions I loose the files. The planner still shows them as existing, but when i try to open them in the planner or via the "recent files" option, the preview only shows a window with the name of the file.

The correct file still exist on my other device (when the problem happened during synchronisation) or on the original date in the planner (when it happened during the copy process). 

Is there anything i can do about it? It is very annoying to always check if all files exist.

Hello HL,
 Are you editing/annotating those files by any chance?
 There is a bug in iOS/macOS by Apple that we're trying to patch but it is related to annotations.
 If you can provide additional info, please do so to support @ idoceo.net
EDIT: Another question, have you verified that you have available empty space in your iCloud account?

Thanks for the fast answer. My iCloud still has 2.1 gB of space and stores other files without problems. The problem also appeared with original files without any form of editing. I guess i will write an email to the support than.

It's me on support as well HL, just drop me a line if you can provide some additional info so that I can reproduce it on my side.