Thanks Kelly, to answer your questions
1. Yes I stay logged in during the entire edit session. One troubleshooting method I tried was to log out of online and back in during the edit session, that was unsuccessful.
2. This is with Arcmap 10.5.2.
3. I have only a vague idea what the REST API is, so I haven't tried any troubleshooting involving that.
4. This is a problem on my machine, I've thought that for a while, but I'm not sure where to start troubleshooting.