Cummins grid heater spiking voltage?

My trailer is lightly used and I have already had to replace the LED brake and running lights. Today, I replaced all my amber LED marker lights which were obviously smoked. I have an 04 Ram and am wondering if the truck is sending an over-voltage to my running lights.

When I cold start the truck the grid heater will cycle causing the headlights to dim and the fan motor to slow. In a minute they will speed up and brighten. This is from the outset even with new batteries. Would this voltage fluctuation have an impact on my trailer lights?

Any ideas to protect my trailer running lights? Should I wait for the engine to warm before turning on the lights? Do they make voltage regulators I could dedicate to my running lights circuit?

All of my truck lighting has no issues but is incandescent.