Hotel Hot Water Issues

So we've got a boiler that heats water for the whole building.

Boiler is running good, pipes hot, thermometer reads about 130F.

3 different rooms, across multiple floors and different ends of the building all of sudden have complaints about their showers and sinks only getting lukewarm. One non-guest sink is also not getting hot.

Tested several other sinks and showers, all running fine.

We've had complaints here and there over the years, but typically like one every few months.

Anybody have any idea what the issue might be or at least things I could try to narrow down possible issues?