Inadequate battery capacity should not cause an inverter error. If the battery is fully charged, the inverter should work fine, maybe for a short time, but for as long as you have adequate voltage going from the battery to the inverter, there should not be an error indicated. I'm not convinced CW really has completely trouble shot the problem. I know, or get that you are kind of locked in with CW, but if it were me, I would directly contact Thor and ask them to recommend another shop so you can get this solved.
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