It’s hard to debug this in the abstract, so I’m going to give you some advice instead. The key to figuring out the answer to any problem like this is focus, and process of elimination. Start with figuring out why you can reproduce the issue in production but not in development.
- Are the plugins and the themes exactly the same in production and development?
- Are you using the same kind of user (admin mod etc)?
- Are you performing the actions in the same kind of topic?
- Are you performing the actions at the same speed?
Start by doing all you can to try to reproduce the issue in development, if indeed there is an issue. Focus on that until you get results or figure out why it’s different in production.
Also, part of the reason that the Topic Custom Fields plugin is not intended for production use is that it doesn’t have any tests. I know you’re not going to like hearing this, but you should write some acceptance tests for the composer behaviour. That will give you a definitive answer as to whether it works in particular scenarios or not.