Many issues can occur that would cause a mixer to do any number of things, including firmware versions being out of date, problems with on board scenes on a mixer causing peculiar problems, etc.
The best suggestion we can give is to start a Support ticket with your My PreSonus Account online. Once you have done this, a PreSonus support agent can review your request and present some solutions to the problem. Be as descriptive as possible and provide information as necessary to help explain the situation.