Jack,
I would honestly stop using the modification at this stage before there is any damage done to your Lhires,there is something obviously wrong whilst using the belt and it is twisting the collimator lens support housing somehow. Maybe the threading of the lens housing is different on the newer models of Lhires,possibly a much finer pitch than the original design I don’t know, but if that is the case then the belt mod could be pulling the thread out of the other hence the doubling (distortion) of the lines. Worse case scenario is that the collimator body ends up cross threading 🙁
Regards
Alun