Contributor users can't enter or save data

I’ve been chasing this for a couple of weeks. I have several nodes (`6-7 out of ~200) that take 12-15 minutes to calc a number after input. The application then hangs for 30 minutes before you can navigate again. Anyone have any idea where I can start? This wouldn’t be so confusing if every node was experiencing similar behavior. It appears to be specific to the node and not to the user id.