why is my slow draining tub causing the toilet to bubble and water to leak from the wall?

A month ago we had a slow drain in the shower which leaked water through the wall onto the LR floor and out from under the vanity. Plumber snaked out the roof vent and said to use single ply toilet paper. Now, a month later, the drain is slow and is leaking out from the wall again. I even used caustic professional pipe cleaner as was suggested by the plumber (m. acid) to no avail. Could it be toilet paper clogging up my vent stack? Kitchen and master bath are fine.