Happening only on AC operation then it would be due to a voltage drop BUT with it happening on AC and propane operations it has to be related to installation/ventilation of fridge.
Download the installation manual
HERE and check the dimensions of fridge opening, the proper clearance dimensions, the proper installation of upper/lower vents and the correct baffle installation.
Something is not right with that install. Maybe it isn't properly sealed allowing outside air flow to the inside of RV around/under fridge when you turn on A/C Unit disrupting the natural draft across the cooling coils