Hi there

Once the line contact comes in are you getting the stated voltage on both sides of the line contactor power terminals?

If on one side you have full battery voltage and the switch side you have the stated voltage then it must be bad tips. ON the other hand if you have the 12/18 v on both sides then you need to trace the supply back to the battery and make sure the battery itself or connection from the battery to the controller side is ok? Sounds like a battery problem to me or the line contactor itself.