回複：my understanding is there is no shower pan. It is tile on the

Likely it is all title. If the bottom is shower pan it it is dificult to leak. 

The worst thing I would do is to cut the grout using 4" hand saw first then grout remover saw and re-grout it. This will be a no more-than-3 hour job for a professional with essential tools. Re-tiling the whole thing is safer but I think it is not neccessary.

 

I fix the same problem as I described and no leaks ever since.