Last year I had a walk-in bathroom done in a condo that is used as a rental property. We had issues with leaks and had to have the bottom 2 feet and base replaced twice. It was finally completed with no leaks. One year later, I just noticed that some of the spots where they put sealer in the soap dish niche and in several spots around the floor (about 1.5 feet long) were deteriorating and exposing holes in the grout line (the sealant was peeling away from the wall/floor joint). I brought back in the contractor and we agreed to replace the sealant with real grout. He did this (he did mention that it might have a tendency to crack but we did it anyway). And the new grout (haystack color) cured fine in the soap niche to match the rest of the shower color. However, in the two 1.5 feet spots on the floor/wall joints, the group did not cure (it's a very dark gray color). It was only left for several days without water to dry as we had a renter come in after the 3rd day. However, when the original job was done, it only took several days to fully cure. I suspect that it was water behind the wall that might have caused it to not cure. I suspect that because when I scraped away the deteriorated sealant in a spot and used a fan to dry it, it still show signs of water when I pushed a tissue in the exposed grout hole after the fan was on it overnight. My plan now is to have him take out the grout that would not cure (is this possible and not destroy the tile?) and then replace it again and leave it for several months to dry fully.) Would you recommend any other solution? Also, if there *is* water finding it's way under the tiles and keeping that joint area wet, I assume we have to fix that as that would over time weaken the tile base - correct? Thanks much for your help!