My house was built in 62, with cast iron pipes. They failed and I had them re-lined (CIPP). My guest bathroom backs up to my master bedroom closet.
The other day when the kids were in the bath, I noticed water on my closet floor. I assumed it was the drain, so I cut a hole and installed an access panel so that I could swap out the drain. Done, no leaks, until everyone took a bath, then water again.
I left a camera there as it would only happen when I wasn’t watching it. Then boom, water was coming up from around the PVC waste pipe. No clue what to do now.