We just moved into a new home about 8 months ago. Soon thereafter, we found some soft sheetrock at the corner where the tub/tile interface meets the sheetrock (see picture attached). We recaulked with sanded caulk and covered with clear silicon. Regrouted all tiles and resealed the grout. Also replaced the shower door.
Soon thereafter, the other bathroom that is built in the same manner, developed a leak in a similar location but on the back wall. We followed a similar course of action on this bathroom.
A few months later an both are leaking again in the same place. A moisture meter indicates roughly 20% moisture at this point (where the rest of the interface up and down the wall is roughly 11%). Both tubs are level end to end but canted very slightly towards the bathroom.
Removed back sheetrock behind both leaks and saw no indication of any plumbing leaks or other sources. Had the builder look at it and a couple other plumbers who said to recaulk which we have already done.
From what I can tell, water is getting into the grout and tileset and migrating downward and towards the edge of the tub. It is seeping through this interface and gradually wetting the sheetrock.
Any thoughts on what to do here?