Threading Index Varies With Speed

I think github.com/LinuxCNC/linuxcnc/pull/4453 alleviates the issue, testing on machine needed for anyone available to do so

Thank you so much for looking in to this.

I'll test in the next few days on my machine and report back.  You want results here or on GH?

GH, I don't get the email notifications here, and I have to remember to check