X Axis Motor issue.  

X Axis Motor issue.

I am running a MK2.5 that is close to 3 years old now.  I have recently been having issues with layer shifts on the x axis.  I tried tightening the belt but then the x axis motor started loosing steps, making a grinding noise.  Even without the belt in place the motor seems to have a very small amount of torque.  I also notice that the motor makes a small amount of sound even when the axis is not moving.  

This behavior is similar to having a couple wires reversed on the stepper.  I am operating on the assumption that one of three things:  1. The motor itself has failed (unlikely), 2. The wire harness is bad (possible, maybe) or 3. The Rambo Mini is going bad. (most expensive).|

I have ordered a replacement motor and wire hoping that one or the other fixes the problem, and figuring I will put both to use, sooner or later. 

But the possibility that the mainboard is going out has me concerned.  I should add that I also had a hot end short that popped a 5A fuse just days ago.

Are there other possibilities that I may be overlooking.  Should I check the stepper current level?  Not sure why or how that could change...