If you plug an RV into an outlet all the time without shutting off the power first, there is a momentary inrush current caused by the converter which creates pitting on the plug blade and the contact surfaces inside a receptacle. Over time, there is more and more pitting and "dirty" contact surfaces that causes resistance and thus heat. In some cases you can end up with a meltdown.
Check the plug blades and if not clean and shiny, clean with some sandpaper. You can't do that with a receptacle so it would be a good idea to replace it. Can't see inside a recept. either to tell how bad it is. The best thing you can do at home is install a disconnect switch next to the dedicated RV receptacle. At a CG, always shut the power off first before plugging in. Newer pedestals have a label on them telling you to do that. If a CG 30 amp recept. looks really bad I have a Camco 18" 30-30 adapter so that if the pedestal recept. and adapter do go up in smoke only the adapter will be lost.
Using a 30 to 15 amp adapter and especially if using a 15 amp extension cord can get you into trouble due to bad contact between a plug and receptacle/connector. "Puck" style adapters are particularly a poor choice as the plug and receptacle side are so close together and more susceptible to heat damage. Poor connections can also increase voltage drop and if trying to run an AC unit will cause a higher current draw, more voltage drop and more heat until something gives out.
Having a voltmeter permanently mounted in your TT is one of the best "tools" you can have. Plugging an RV in at home and trying to run an AC unit or high demand appliances isn't a good idea unless the circuit is 30 amps - wire and recept. You'd also do well to check the voltage at the receptacle the TT is being plugged into before and after RV loads are turned on.
As bit of an aside, RV adapters are a kinda odd thing. They don't come under the NEC but UL, ETL or CSA standards. Can't connect a 30 amp load to a 15 amp circuit under the NEC, but you can with an RV using the right adapter. Some of the various RV adapters don't make sense but they are permitted, including for marine use.
Anyway, hard to say exactly what the OP's or friend's "simple" issue is without more/correct info.