Contributors Unable to Submit Posts

Contributors on my production WordPress blog are unable to save drafts or submit for review. Autosaves still work, but the button presses do nothing. With WP_DEBUG_LOG set and web proxy tracking I am not seeing any helpful errors. I have a development server hosting a copy of this blog with the same version, theme and plugins and I can’t replicate this issue there yet.

For now I have my trusted contributors at author level while I am trying to figure this out. Does anyone have troubleshooting guidance?

[Moderator Note: No bumping. If it’s that urgent, consider hiring someone instead.]