Hello Toreto2015, here in my country when it is like this, he is said to be crawling, that means that the mason did not place enough mortar or glue in that area and is obviously hollow with air, of being a ceramic majolica with the own body weight or Some heavy object that falls in that place is synonymous with cracking, the definitive solution is to remove that mayolica and paste it correctly, settling with a rubber hammer. If you always remember the place, try not to step on it to avoid cracking while you are looking for a way to get someone to fix it. Now eat is a large piece of fact that when you take it out there will be some damage, but a good master bricklayer if he manages to take out in an optimal way with the least possible damage, I would recommend you not to step on the spot and inform those who use that service the care that does not step on there to avoid possible cracks, although as it is fiberglass it can resist at first but it is not something safe the best thing would be to correct even if that implies expenses, there are products and resins that can fill those voids through an injector, but it would have to be seen how to get to that site with the least possible damage and evaluate the possibility of not removing and repairing it in the same place.