Hole in screed (8mm wide, approx. 8mm deep) in upper screed layer

Thank you for the feedback. I sealed it with quick-setting cement. The working group for root cause analysis seems absolutely justified to me – suggestions for which industry experts would be suitable for two to three opening speeches at the event are welcome...

A hole is a hole is a hole – as long as you can't see through it, I give my ok to ignorance ;)