During a carve my Z axis dropped into the table and wont move up or down but makes a loud hum like it is trying to. Removed belt and same thing and also with other steppers. Sounds like an XController issue? Any help would be appreciated.
Something is probably mechanically preventing it to move.
It’s doing the same with a new stepper just hooked up and not connected to anything.
I agree with @HaldorLonningdal sounds mechanical. Did you try turning the pulley by hand and bringing the z up?
It does it with any stepper connected to cable and not to any belts. Figured it to be the motion controller and just a bit ago inventables support called and confirmed this.
Thanks for the input guys
Inventables got you covered then 
What are your GRBL parameters BTW?