Judging from the amount of water in the street and the fact that he's taken the back off, I'm guessing that he's already washed the inside of it.
I had a mixer that was wet two days in a row each morning, I had suspected the leaking tent, and condensation, though I had covered the board.
On the third day, a few channels started flaking out and the board started making noise on the main outputs.
Got a spare board in place, took the mixer out of the case and found the case had gallons of water sponged in the foam on the bottom, and water literally poured out of the mixer.
Turns out sprinklers in the tent had been coming on each night and spraying the console from underneath, the board cover had directed the flow in to the case.
It took three days for the corrosion to start, if the hose jockey in the OP does properly dry the board off before start up, all may be well, or better than it was