No databus communication. 2015 Coronado.

Driving in rain, for a few hours, then dry for a few more. No engine shut off during this time. Found a place to eat and sleep, turned key off, engine stopped, but dash went nuts. Gauges cycling as though the key was just turned on and the ecm was self testing. Couldn't get a lot of them on video as the timing was so inconsistent. But I did get this quick few seconds on video.
I pulled the key, turn off everything, and unplugged every item including the phone to see if something was back feeding power, nope. Turned off the battery disconnect to quiet it down and shut it up. Let sit for a few minutes, then turned on batteries. Same thing, only slowing and stuttering as though it was fixing itself. I let it be with power on for a few minutes, and it kept getting slower until it finally went quiet and all gauges were normal for being powered down.
Stayed quiet for most of the night, but fired up the diesel bunk heater and a whole new alarm and set of lights went off. Shut down heater, no change. Shut down batteries and let be for the rest of the night.
Morning came, all good, key cycled correctly. All gauges good, everything worked as it should. Hit light rain again, but enough to be splashing with the tires, next stop, shut down and....the dash went stupid again.
Must be moisture issue, but where would be the common FL place to start so I can go from there? Thanks.