Check Tub Spout and Overflow

What happens here

Prior to cutting into the wall, perform additional visual checks on other common leak points. Inspect the tub spout where it connects to the wall, ensuring there's no water seeping behind it. Similarly, check the overflow drain cover and its gasket for any signs of leakage. Water from these areas can often run down inside the wall and cause damage similar to a valve leak. This comprehensive inspection helps rule out simpler causes before resorting to invasive measures.