jeepsr4ever
Before you hit REF and have to loosen your gantry to take the tweak out of it listen up.
You need to make a change in motor tuning. Even though your A may be slaved to your X (in 4 axis boxes only) you still need to input a steps per, accel and velocity that exactly matches your X axis. Failure to do so will cause your gantry to bind and you could shred a gear. REF is used when you install a home switch. We find for 99% of cutting a home switch is not needed. If you do install one MAKE SURE you have the slaved axis setup in mach motor tuning.