No Inverter charge with shore but OK with genset

[cmillsap]

I'm not familiar with the M450's Multiplex system but in looking at the schematics, the 120vac power sources (Gen & Shore) through the transfer is typical. So the inverters/chargers don't care which is the power source and should work the same on both power sources.

If the Genset is supplying a strong 120VAC and everything works as it should, I would question the power supplied from the shore post.
I would try another shore power source before I would tear into anything in an effort to "fix" the problem. The bus may not have a problem.