Viewed a job this morning, , grout is cracking, customer wanted to know if grout could be scraped out and replaced, he thought it would be a small cheap job, on further investigation we found out so called tiler had tiled directly to plywood in shower area and onto floor with UFH (underfloor heating) i removed tile on shower wall, looks like its been dot and dabbed, whole lot in shower wall area needs to be removed and all the floor needs to be removed, this will mean trying to remove glass shower screen without breaking it, removing toilet, removing all controls and shower hose, destroying existing UFH and replacing with proper materials.
Do it properly in the first place and avoid these costly errors, builders please stop using plywood to tile onto, this can be the result. Now you know why tilers moan all the time!