Most likely it’s his own fault, I didn’t feel how I hit the reinforcement, but it seems that they are intended for this, they didn’t press for a long time, I don’t know what the reason is, the tar, which the builders used to waterproof the screed, clogged the drain grooves and the drill is trite overheated. But with a small 6, this was not the case; I made 10 holes in the same coating for her and everything is fine .