That is a real shame, I have been on the Harz system a few times and it has always been fine. Like one of the above posts, I was on a train coming down from the Brocken when the loco failed, but they sent two locos up with a train coming from the bottom and one of those detached from that and was shunted on tour ours and took us back down. It was fine. I hope you try again with success next time.
We had a problem with with the steam loco at the top of the Broken. After sometime a diesel railcar arrived, I presume carrying fitters. Eventually we got going but had lost our path. We were a charter train so we not a full length train and were therefore able to tuck into the passing siding behind a service train to allow an up train to come up the hill.