iWork and iCloud drive on my iMac seems horribly unreliable. Things work for a while then I can't open files. let's say for example, I have a Numbers document called "spreadsheet.numbers" every once in a while when I try to open that spreadsheet on my Mac I get an error message pop up saying: The file "spreadsheet.numbers" couldn't be opened. and the dialog box only has an "OK" button. once this happens, I cannot open any existing iWork documents, nor create and save any new ones to iCloud. I just get these "file couldn't be opened" errors. the only thing that seems to remedy this is to go to System Preferences and turn off iCloud Drive, and agree to delete all iCloud Drive documents on my Mac. I then turn iCloud Drive back on, and give it a few minutes for the documents in iCloud to re-sync to my Mac. After that I can then open my existing iWork documents and continue working. Everything will work normally, for a while... --- until the problem happens again some random amount of time later when I once again can't open an iWork document. Turn of iCloud Drive, delete files, turn on iCloud drive... repeat. Very frustrating. anybody else see this? more importantly, is there some fix?