My question involves real estate located in the State of: Michigan

I sold my house in April of this year, and am now being told by the buyer's agent that they are looking to see what recourse they have for the following issue:

Prior to the sale, the buyer's inspector noticed a leak from one of our showers. I had a plumber take a look at the leak and it was determined that the leak was coming from an opening in the floor where some of the grout had deteriorated. I re-grouted the tile, and during the final inspection, the buyer, and presumably the inspector ran the shower for 30 minutes with no leaks.

Now, the shower is leaking, 7 months after the sale, and the buyer is saying that their plumber needs to tear out the floor for several thousand dollars.

Does he have any recourse to take me to small claims court to pay for these repairs?