I have an LC-40 with dual turrets. When I try to move the lower turret in the +Z direction, I get alarm that says

"100-6 Alarm A DIF over ZB-Axis 4380"

Anyone know what this means? I'm guessing it's not getting feedback from the encoder or something? It moves fine in -Z (well its on the limit and doesnt error when you push the button to move more in -Z, anyway), as well as working fine in the +X and -X axes... just this one motion that causes a problem.

Anyone got any info they can share or know what the error actually means???

Thanks!

From my experience you have a damaged servodrive board
check your motor leads resistance to ground, must be "infinite"
I mean if you use digital multimeter you must read OL from the leads to ground or chassis.
On the other hand you can swap drives after this test and see if problems persists in the other axis.

Thanks, I will give it a shot.

The previous owner of the lathe said he thought it was a servo driver board, but I think he was just guessing :) Thanks again!

This means that whilst moving, the actual position and the expected position have gone outside of the allowable range, e,g, servo lag.
If you have LDUTR drives, on the servo page of the check data, you will see an ODIF value. If at jogging at 100% this exceeds 0.050, I might be wrong on the decimal point, but just read the figure displayed, ( it will initially be high on moving due to axis accelerating to speed), then your servo is incorrect.
This should be a + figure jogging +, and -jogging -. Before adjusting ensure the slides are receiving lube oil, or this alarm can be generated due to stiction.
Adjust the gain pot to get below this figure, or as close to it as possible. As you adjust you will see one direction decrease and the other increase, you are basically adjusting a band sideways until the centre point is as near to zero as you can get it.
You can also get this problem on these drives, after a period of use, if the heat sink compound between the transistors and the heat sink is old, hence the more heat generated, the less responsive the transistors get.
I am sure it is the gain pot, accessible through the cutout in the smoked plastic cover.
The easy test is swap the top boards between drives, set up as above, and if the fault moves, then the board is faulty. Ensure any DIPS are set as per the boards you swap.