Well, I guess the first thing is to try to minimize any connections/splices by reworking/redesigning the harness.
If splices are necessary, I would cover the splice/soldered connection with shrink tube. The stop circuit has about 175 volts, which is always looking for a quick trip to ground. Plastic butt connectors, especially in a damp/wet (especially salt water) environment provide a great opportunity for shorts to ground.
The 12 volt side is less of an issue, except in salt water.
I realize that soldering is not always a possibility, some wiring has a strange coating on the copper core that actually resists soldering. They do make metal splices that don’t have the plastic sleeve, making it easy to slide the shrink tube over the splice for a nice sealed connection. Just don’t be like me, and forget to slide the shrink tube over one of the leads before making the splice!
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