If you look at his diagram on his post #56, there is a remote switch that should be powered by his original DC Panel.
For my clarity of thinking there are 2- DC Breakers.
1) Original Panel DC Breaker or lets call it
OB
2) The Parallel Panel DC Breaker by Blue Seas or lets call it
PP.
Also noted, it works great when
not at anchorage.
So there has to be a cross connection somewhere.
This leads me to the Battery Charger or Shore Power vs Anchorage.
I suspect the PP breaker is the issue as
@Maine Sail noted.
Jim...