[LoneWolfGal]

Post mortem: The most likely way thread damage could occur in the middle of the rod is by tightening it to the limit of compression and then continuing to tighten it. But I was aware of the warnings not to overtighten it or risk breaking something on the VarioCam. I estimated the unit was compressed no more than 90 percent, judging by the tautness of my chain compared with the laxity of chains in videos I've seen. If I had reached the compression limit, I'd think I would have felt some resistance, more than when just tightening the nut. Perhaps the progressively increasing force required to tighten it was just too much for soft threads to handle and they gave out. That said, I have to acknowledge the possibility that I overtightened it, despite being very careful not to. Regardless of the cause, I'm going to need another compression tool. First, I'll see what the company that sold me this one has to say.