I have been running an experiment using Otree for several days now. Today there was a session wide blackout, and all the users saw an 'application error'. Since the same software worked perfectly in previous sessions, I suspect this was an error on the server end? 

I have no idea what to do to prevent this from happening again! 

This is the error/issue I see, as it is reported on Sentry: OSError asyncio.selector_events in write_eof
[Errno 107] Transport endpoint is not connected

I have attached a picture of some lines of code that Sentry has highlighted. 

Has anyone had this problem before? Do you know a solution to it?

- Can you provide the full traceback? (check in Sentry if there is a way to copy/paste the traceback as raw text, or collapse all the code snippets so that you can see a listing of all the code lines).
- Are there any other errors in Sentry?
- what version of oTree?