Closed loop doesn't work

[RbAstra]

Hello

I want to control 3 axis by sending Grbl commands in the USB port by using pronterface software. I succeed to move every axis but I need to be sure of the position (closed loop).
So I rebuild 3 magnetic encoders (V1 with Atmega) by using the manufacturing files and soldering components on the PCB. I made some tests with the encoders and I can measure the position of the system (M860 command) but it didn't work in closed loop.
Received value in ticks :

This is what I've done to verify closed loop function:

1. I send a GRBL command to make relative positioning -> G91 G0 X100
2. I block the system during movement (just like the video at the bottom of the encoder wiki)
3. Thanks to magnetic encoder I measure position in ticks at the end of movement and the reached distance was 97mm instead of 100mm

When I enable the correction (M867 command) it responds the correction is enabled for all axis. However it doesn't correct the position. And the returned position doesn't include home offset.

I'm using Marlin 2.1.2.1

Does Somebody know why ?