Light troubles

[Idalogger52]

Hooked up today for the first time since fall, turn signal issues with the Montana (2015 3155RL) when pickup lights are off the coach turn signals work but look dim. When I turn the truck lights on I loose turn signals on the Montana, the tail lights work and are bright but no turn signals. Any ideas? I would think a bad ground would not let the turn signals work at all, but maybe I’m missing something.