Well a head scratcher to keep the grey matter churning. Are you sure the DW doesn’t have a master remote hidden and is turning all TVs off on you? April 1st is coming up fast.
The original post says all three appliances turn off after 30 minutes.....fair to assume at exactly the same time? Sleep timers are not set on any of them. Can we assume all three TVs are on an inverter fed circuit(s), but they only shut off by themselves when running on normal AC power sources from shore or generator (which should normally just pass through the inverter transfer switch) to the TVs. The TVs don’t have any problems shutting down in 30 minutes when shore or gen are off. So inverter running off batteries runs all TVs fine with no shut offs. So if its not the DW......then it is something cutting off the shore/gen AC feed to/through the inverter. The inverter AC output should kick on when the normal sources are shut off. I doubt it is the coach shore/gen AC transfer switch, but is there any device like a permanently installed Progressive Industries (or other vendor) AC power line monitor between the AC transfer switch output and the converter AC input? I think the progressive boxes do have delay timers but typically a couple minutes delay cutover only for generator startup delay. So basically you have to keep the DW in the same room as you with hands showing when the TVs shutoff again.
A good one for sure but maybe there is some info missing or incomplete?