Hi, we have had our solarium steps and terrace tiles redone 3 times due to damp in our apartment. Last time was a few weeks ago when we were last out. My husband tapped a screwdriver over all of them and was able to tell the ones which had not been sealed properly underneath. They were very quick to come out and fix, we just marker penned the ones we were not happy with. I'm sure they'll sort them for you.