Thanks to Darran, bulldog2k, james.welsh, Mox and aaa who posted to help me answer this. I went back to one of my playing partners and he checked his rulebook (in German) and agreed with us that I did NOT break a rule by taking a practice swing. He will pass the message on to the other players involved. It seems that they were confused about practice swing versus practice stroke.

Thanks again for helping me out.

Ken