I do not know this winch co. but when you rebuild the solenoid box, if it is so called weather proof, it could be generating condensation in the box (hot then cold) and no way for evaporation. It will be wet or slowly fill with water.
Under the hood is good, and if the box has air vents (openings) on the high and low sides (a hole for drainage and a hole for moist air to rise) it will stay dry inside and useable. With the exception of this box being under water when winching.
The difference between WEATHER PROOF & WATER PROOF is a BIG difference in the construction.