On your bad unit, I would disconnect the AC and DC power feeds from the upper power module. They are spade connectors on the left side of the modules. Make sure those feeds are taped up well before re-energizing. That should remove the problem module and hopefully allow your DC breaker to stay on. You won't need to disconnect the communications ribbon cable either, since the module won't have power. If the unit powers up, it'll complain about the missing module but will do about 2600W with the remaining module.