Hi @Dave-B -
Welcome to the forums!
See this recent thread that may be relevant for your situation - disabling the pre-arm checks should be an acceptable workaround. The root cause may be a poor compass calibration (complete this in an outdoor area, far from anything), interference at the place you’re operating, or the batteries and connected cables shifting inside the hull vs. their position during calibration.
Ships and areas with lots of steel or electrical power transmission can definitely cause issues!