Are we talking about buckling due to moisture in carpet?
If that's the case, it is an installation issue (It was never power stretched properly, in other words- the carpet is larger than the space it is covering.)
If that indeed is what's happening, I am willing to bet that the re stretch was done with just a knee kicker. As otherwise they would have needed to re cut in doorways etc which gets complicated. And if that is the case it may buckle after you clean as well. Normally it will go back after a day. and lowering moisture and drying it fast may help but not guaranteed to prevent it. Particularly with an owner that by now is super aware and concerned about it.
You may also want to know with what products was it cleaned before. I apologize if I was preaching to the choir. And yes- Good luck
