Just for info:

Pianos are tuned by twisting a steel pin that sits in a wood board.

Old pianos sometimes have the holes enlarged, or have small splits in the wood, and won't hold a tune, the pins will untwist under the tension of the string.

One cure is to remove the pins, redrill the holes, and install bigger pins. But that's expensive and many pianos aren't worth it, or the board isn't in good enough shape.

Another cure is to tip the piano over so the board is flat, and drip a bit of crazy glue into the base of each pin.

It has to be very thin glue.