I had the same issue, and I also believed it was resolved by uninstalling completely the plugin. Disabling it didn’t fix it.
I believe it was, in fact, because I uninstalled the onebox assistant. It has been some days ago and I can’t be 100% sure, but my issue was identical to yours, so…
Also, it is possible that my screenshot of installed plugins falsely shows what plugins were actually installed when the issue occurred. What I’m sure of is that the issue didn’t resolve after just rebuilding, onebox assistant was disabled for more than a year, and I didn’t do anything else than remove it from app.yml. I might have taken the screenshot after this rebuild and before testing again…