Model checker - fails to save excel file.

I'm running Model Checker on a BIM360 session for about 30 models. Maybe 1/5 of the time it closes the task with the error "Unexpected Error: InvalidOperationException: Error saving file [PATH].xlsx". This happens on different models every time, the path location is on our server. I've tried breaking the task up into smaller model groups (4-5 models at a time) but still get the error. This also happens occasionally with html files, I'm exporting both.