A couple of months ago, I began to have issues with Google Drive sync errors - recurrent errors like: "google drive needs to quit - an unknown issue occurred - code 2281" - Google support was singularly unhelpful in solving the problem, but I did find a solution eventually after first trying a host of bad suggestions from Google Support or people on the Goggle Drive Help Forum. By scrutinizing the Google Drive sync log file, I noticed that it called out the path to a file that it tried to sync before the application quit. It was a pdf in one of my Paperpile folders. The file had unsupported characters in the filename indicated by black diamonds with question marks inside. I deleted that file from Paperpile, from the Paperpile trash folder, from my Google Drive, from the corresponding online drive folder, and from the Google Drive folders on each of my other computers that were being synced. All was fine after that. That was a couple of months ago. Then, just a few days ago, I started getting the recurring sync error again. The log file showed the telltale error: "Exiting due to critical failure: TypeError('must be encoded string without NULL bytes, not unicode',)", but I couldn't find a path to a bad file. I checked my online folder and to my surprise found the same bad file that I had cleaned out and removed successfully more than a month ago, now present once again in my Paperpile "Trashed Papers" directory. How strange. I don't know if the file was restored by Google Drive or by Paperpile after being gone for more than a month. Very odd, and a huge waste of time. I deleted all the entries in my trashed papers directory (again) and that seems to have solved the problem. Would it be possible for Paperpile to reject files with those unsupported characters instead of cataloging them? Does paperpile introduce those characters? I know that others have had similar problems, since I read a forum post from someone else who also identified a paperpile pdf file with the same characters as the culprit that caused GD syncing to fail.