That spindle isn't suitable for rigid tapping. If you run it under 6000 rpm, you may damage it.
First "ger21" thank you for your support and finding errors in my ideas
"12 steps" - 1st We admitted we were powerless without knowledge !!!
I did contact manufacturer and ...
They are really helpful and supportive but I don't think they ever did this kind of tests.
I have an arrangement that I will do tests and if I damage spindle they will be more than happy to take it for an autopsy and warranty replacement.
So the plan is simple: squeeze sh.. out of the spindle and see what happens
I also did get more info about encoder: