My (non-PM but Taiwan) 14x40 has a similar characteristic where it likes to be fed the engagement leaver a 'line width' ahead of the actual intersection. Not sure if that's just reaction time or mechanical. Looks like you have a rivet for a center so you may have to experiment till you find the special spot LOL. I think its classic offshore machines that they put a half decent graduated scale on & then just hammer down the opposing center mark TLAR +/- a wide margin. I wish they would just put an adjustable scale on one side & leave the tuning to us.
Another thing I'll throw out. I had to disassemble my apron I had the threading lead screw, power feed & fwd/rev switch bars all off. When re-assembling I thought hmmm.. now what if the threading lead screw were rotated a half turn before being pinned in the output coupler, would that not shift the threading dial phasing? Fortunately my roll pin hole looked like it was was drilled off center 'by eye' so there was no chance the roll pin would even engage if rotated 180-deg. It could only go in the one way. So maybe this was by design intention? Normally I would give the benefit, but seems like every shaft with a roll pin was a similar off center unique hand job, which makes parts replacement a real PITA. Anyway, something to check if you ever pull your lathe apart.
Oh, and I discovered I had a steel roll pin instead of a brass shear pin so I made one. Make sure its a decent fit, not hammer in tight but also not loose so you don't introduce the equivalent of backlash. I've heard of other stories where its a taper pin drill but they have a steel pin in there because brass taper pins are hard to find & 50/50 chance its its metric.
I'm kind of like you, been using the lathe for a while but just not that much threading. I bought some inexpensive Ebay internal/external tool holders that look to be based on Carmex. They seem pretty decent. A few practice runs & parts came out pretty decent. Now I am actually quite excited by all the things I want to make with threading features. It is rather contagious.
A few amateur tips I can pass on:
- you must have a reliable way of measuring pitch. I have the 3-wire kit but I seemed to be fumble fingers holding the buggers on, at least fine threads. I have an older model Fowler screw pitch micrometer with the anvil kit. Personally I find that much easier & more reliable. If I did it again I would buy a Shars digital because then you can buy the metric anvils, switch the display to mm & now can do both imperial & metric with same unit. The big name thread micrometers like Starrett or Mitutoyo are brutally expensive new. Used ones are always a crap shoot, maybe sure teh anvils are included or you are confident you can get them.
- I found threading is a bit like boring with respect to taking a few spring passes to be sure the depth is consistent before measuring. There probably is a progression formula somewhere but if DOC is say .025", the first .015" is nothing, very little removal. Its the last 5 thou where more material is coming off = more depth on the face of point tool = more propensity to deflect = reason for spring/cleanup pass. Good luck!