Stepper shakes when it normally stand still

Hello,

I use 3 picstep drivers for my CNC machine. They have done their work very well! But when i started my machine today my Z-axis stepper was shaking. And is not turning correctly.

I don't have a scope at home but when I touch the switches wich set the stepmode the shaking stops, and returns after a while or when u want to move the motor.

But when i measure out that circuit nothing abnormal shows up...
could it be a LMD thats damaged? I use 8k for the current resistor.

My take on this is when you have a problem and you can touch, push or move a component or wire and it changes the problem it is probably a bad solder joint.

budP