Leak in bathroom ceiling from upstairs shower
We have a slight leaking problem in the downstairs bathroom ceiling last year and the homeshield contractor came to check it. We were told it was not a plumbing problem and the water coming from the shower upstairs. We did the caulking as suggested and the problem seemed to go away.
Recently we found some fresh water stain (about 3-4 inches in diameter) and we thought it was time to do the grouting/caulking again. To make sure it was not the draining pipe problem, I poured about 3 gallons water into the hole and didn't observe any water leaking downstairs. That encouraged me to spend half day looking for tiny holes/cracks on the tile wall and fixing them.
Today, after 72 hrs of caulking and grouting, I used the shower again. The water seems to find a shortcut to go through the ceiling. It not just leaks, it rains! I tested the draining hole again, and this time the leaking on the downstairs bathroom ceiling started almost immediately.
My question is, does this mean there is some pipe problem, or do I need to replace the whole shower basin?
Thank you so much!