Jerky movement with X servo : Precix 2100 series with LinuxCNC

I am stuck with a X Servo that has a jerky movement (Jog and G1).The original controller was updated with a computer and LinuxCNC V2.8.2-8. Getting it up and running was difficult, but everything is working again except for the X Servo : its movement is jerky, and the motor makes a grinding noise (not smooth). It seems to be a conflict between acceleration and braking. I've changed several parameters in the .INI file, the movement has improved but I'm stuck. Copley drives were custom-tuned at the factory specifically for Precix servos. However, Copley can't help me. Has anyone else experienced this problem or know which parameters to adjust to fix it? Is the Colpley drive the problem? Here's a summary of the CNC :    CNC : Precix 2100 (DC3 BR)
Controler : updated, Linux Mint 19.3, LinuxCNC V2.8.2-8 + Mesa 7i92 + Mesa 7i77
The Y axis is perfectly smooth.
The X axis is the only one that is jerky.
The servo motor appears to be a SEM motor.
The amplifier is a Copley 4122CE.
I am running LinuxCNC V2.8.2-8I am joining the HAL and INI files... if it can help! Thanks in advance!