Automatic Transfer Switch Failure

X2 on the loose terminals. Transfer switches in RVs are notorious for starting to buzz as they get older because road dust and dirt get between the metal armatures preventing them from sealing up tight. The resulting vibration loosens the terminal screws and soon after that the burning starts. Good annual maintenance should include at least tightening the terminal screws and even better taking the relay apart to clean the moving parts. Alway make sure you are unplugged from shore power, the generator is not set for autostart, and the battery switch is off the make sure your inverter doesn't start making AC!