Everything is at default settings, no collision.
A pure up direction will produce no SMC:
Nudging it with a bit of any other direction works fine.
This only manifests for Z, pure X, Y works fine… Any ideas what could be causing it?
Tested it and have no idea. I know that’s no use to you, but just wanted to let you know your question didn’t just fall into a black hole…
Ha, thanks! I’ve looked at it for 2h+ hours and have no clue. I’m fine with adding 0.000001 to X, no one can tell anyway ;p
I just found it quirky.
Alrighty, the bug has been backlogged for over 3 years now 
And the original post:
pfffff…