Yes, I still have the steppers as idlers. I'll see if I can remove some of the magnetic structure so they spin freely and see if it makes any difference.
If those gaps were skipped steps, it'd take about 20 skipped steps to make a gap that size.
Multitasking PC: I think that'd be a more random occurrence, and I dont think it'd happen at exactly the same time, every time.
Belt jumping a tooth, possible, though not exactly sure how I can test that. Are my belts better off tight enough that they don't sag much, but not stupid tight, or stupid tight?
Cheers,
Dan