Ben, Hi
Thanks for posting your questions.
Sadly the more experienced readers of Ujals excellent site would require a bit more detail before being able to help you.

Could you begin by posting the manufacturers name and model type of the dimmer in question.

Also, I would encourage you to read the technical explanation of the DMX lighting protocol listed elsewhere on this site.

In a large number of cases that wiring or termination errors are the cause of the sort of intermittent problems you have mentioned.