I do not have any experience with that error, but searching the forums I found these threads that might be helpful:
[SOLVED]: Prearm Internal Errors 0x800 - ArduRover / Rover 4.0 - ArduPilot Discourse
If you search for 0x800, you will find a few more. If one of those is similar to your issue, but not exactly the same, you might reply there with a question.