Nowadays they install showers with cement board so this is not normally the issue with a newer shower but they used to install showers with sheetrock. The only thing holding the tile to the wall is a piece of paper and if any of the grout is missing and water gets behind your walls the tile could easily become loose and more grout will come out. This will make more water come behind your walls and eventually make the sheetrock rotten
These repairs are difficult and take a lot of time
We have to try to get as many tiles off as we can in the affected area without breaking any. Then we take out the rotten wall. After that there might be some more tiles and while we have to take out because we need to get back to a stud on each side. Next we install a piece of cement board which is waterproof. Finally we clean up your tiles the best we can to try to reuse them because they’re probably discontinued and you probably can’t buy them. And then we install your tiles back and put the new grout and finally we install the caulk