This thread is valuable and has me making a mental note to be extra careful when I next clean the carpeting.It's more than just condensation. You can see where water intruded through the connector and settled on the board. You guys are getting water under the seat and it's getting in through the connectors. There has to be a water intrusion problem.
I use a small carpet extractor that is primarily marketed for home upholstery cleaning, but is also sold to car detailers. It's very easy to over spray. That's typically a non-issue, but is probably a big deal for the amplifier and cables leading into it.