Our old family room TV at home would occasionally be affected when our microwave or 4-tube fluorescent kitchen ceiling fixture were turned on. A few factors were in play; one, our TV signal is via off-air (broadcast) and the antenna is in the kitchen attic, within feet of the antenna so the microwave and fixture’s startup electric fields could briefly interrupt the antenna’s reception. Two, we are just barely within a very narrow signal path between hills to the main area broadcast towers, so the signal is borderline to start with and easily interfered with by things like fir trees moving in strong wind or a helicopter in between. Three, the TV went through periods when it would not completely receive or decode certain channels, a problem other TVs in the house on the same antenna circuit did not exhibit. Our new family room TV doesn’t display the same issues. I also recently went to LED lamps in the big kitchen overhead, so the old fluorescent tube starters are out of the picture anyway.
In your case it could be a distant signal is just too weak to start with and easily interfered with. Often the opposite is true... if towers are close and the booster/amp is on it can over-amplify the signal. And a weak signal is more readily interrupted by nearby electronic devices like multiplex switches or fluorescent starters, or even some inverters. Now if you’re signal is via park cable or satellite, the issue may be with the TV’s internal components that are supposed to help nullify interfering electrical fields. If the TV is the old NTSC tuner (analog) and needs a converter, the converter may be the problem... some like one I had to renovate had bad Samsung capacitors. I assume your 2008 coach TVs are ATSC (digital) and not in that boat.
Regardless, unless the problem is simply with broadcast distance, there likely is no easy fix.
Joel