Servo problem, get´s a minus value on one axis

Hi all,
I´m new in this forum and really need some expertise help.

We have a machine with an tray stocker.
The traystocker consist of 2 axis X and Y
We have 1 servoamplifier MR-J2S-40A connected to each axis.
The PLC used is a FX1N-60MT-DSS.

Somehow when i was on vacation the X-axis losed it´s position and got a minus value.

I tried to set the zero point again and after calibration the both axis goes to correct position, but when i start the machine the X-axis again get a minus value and only the Y-axis make a movement.

We changed servo amplifier and PLC but the result is the same

Have somebody experienced the same thing or have any ideas what can be wrong, i would be verry happy for help.

//Patrik

Is the encoder/feedback connected to the motor shaft? If not maybe the coupling slipped between the two.

I'm not sure, but if this helps:

The PLC usually reads high +ve or -ve value on a wire break.
So check all your connections again.

Check the torque settings on each amplifier. The low setting can cause the weak responce of the servo. Mits. scailed it by very fanny way - max setting is actually 300%.

you need to provide more information. what is the problem?
negative value is quite common, is this what is bothering you?
you want it to be positive all the time?
or maybe motor doesn't move and do what is supposed to do?
when you say changing plc and servo amp didn't help, did you
test it with current program or one you downloaded before vacation?
do you get any errors? what does diplay on servo amp show on powerup?
can you jog? are the home sensor and it's flag still in the same position?
can you post your program?