My STRONG recommendation is to not use it until you address the problem.
A loose connection at the ATS is an excellent source of FIRE.
Particularly under load, there are a lot of amps running through there. Even moderate resistance from a loose connection can cause extreme overheating.
SO, generator off, shore power disconnected, inverter off:
Remove lid to the ATS. Look carefully for any signs of overheating such as burned wire insulation. If all looks good, just tighten the connections. If burned section, cut it back to good clean "copper" color and reconnect.
Then, look carefully at the contact points. If pitted, probably best to replace. You can "dress them" with a fine metal file. Be sure to clean out the filings.
