@Nicole649 As a remote host, you really need to employ a co-host who lives near your rental and who can be available to deal with any issues in person. As you have experienced, guests may be having issues because they are using something improperly and don't know how to troubleshoot. And it can be difficult, expensive, and perhaps not even necessary, to call around trying to find a technician who can come out quickly to fix something, especially when you aren't even sure what the problem is.
A local co-host can actually save you money- they might see that guests have too many heavy-usage appliances plugged into the same circuit, which is causing the breakers to flip off and advise the guests of what is causing the issue, before it can damage anything. Or in this case, determine that it is the constant AC/heat flipping that is at fault.
A co-host could be someone who does that for a living, another host in the area who might have time to take that on, or even a neighbor. A retired, active guy ( or gal) who is good at handyman stuff and troubleshooting might be happy to be on call for things like this to earn some extra money.
As far as your current dilemma goes, it's tricky. If no one told the guests how to deal with the AC unit, it's hard to hold them responsible. Some people just have no common sense and have never beeen homeowners themselves, only renters, sothey can be quite oblivious and hard on things- they've never had to pay for repairs, they've just called the landlord if something isn't working.
I suppose you could discuss it with the guests, and make it clear you would appreciate and expect some compensation, but with 3 unrelated guests there, who is to blame?
And if you push it, you will likely get a bad review, but that's not the end of the world. You can always respond to a review to clarify things for future guests, and you have plenty of good reviews, so it would be an obvious outlier.
It's a lot of money to eat, but you also might just take it as an expensive learning experience- that you need a thermostat you can control and a boots-on-the-ground helper nearby.