He said that Werner von Braun, and his German colleagues, would be in the concrete bunker watching it all. When there was a malfunction they would start gabbling in high speed German, with one another, gesturing, scribbling designs, etc, which the launch director and others could not understand until they were persuaded to calm down and start the debriefing in English.
I think Gene Kranz covers that story in his book "Failure is not an Option" ...the launch Director in question was Chris Kraft.