Hi, Lokey
I don't think so, Try setting your LowActives as shone in the first pic below, If that doesn't help, Set it up as shone in the sec & third pic's.
All of your Axis LowActives should be the same for Step & Direction State, All "Check" or "X", The only exception to this is if the axis controls are not the same type.
Edit: Also try the Sherline 1/2 step mode 4'th pic, It will increase the Pulse width and give your axis cont. more time to see the pulse's.
It's strange that it's only the X axis, Can you swap the axis cont. boards around to trouble-shoot it ?
Give us a better description of your setup.
Post your G code file.
Chip