Support - Problem with MMBL after a certain number of prints

[jrmartinezr]

Hi David, I hope you can give me a hand.

Look I have a problem with the MMBL, I do everything from scratch on 3 printers.

1. Adjust endstops z, same height. + or- 64mm
2. I install firmware, the commands that you indicate according to the guide.
3. I perform ESteps calibration.
4. Level the bed manually, in the traditional way.
5. Start MMBL and save according to the guide.
6. I restart the printer.
7. I check that the mesh is stored in the printer configuration and it is so.
8. Start printing.

The Problem
After 1, 2 or 4 pieces it seems that the Z Axis goes down, and then I have a very low initial layer.
Or I do the same test that i create, 25 point squares calibration model and in each test, the result can be different.

Printers Configuration

1. In total I am using the Marlin-Ai3M-v1.4.6-XXXXX.hex firmware on three printers.
2. There are two i3MegaS and one i3Mega with the upgrade to S.
   In one the bed is not to warped and if i not use the MMBL, y can get first layer relatively good, but the other the bed are more warpped and need use some MMLB.
3. Each one has 2208 drivers, two of them are using the firmware with the normal connectors and one with the firmware for the reversed cables. Version drivers v1.2 - Vref 0.85.
4. Trigorilla boards v1.1
5. G-code flavor in Slicer: Marlin.

Part of the startup G-code
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
M501
M420 S1
G1 Y0.0 Z0.4 F1000.0 ; go to edge of print area

If something like this has happened to you and you have an idea of where to start reviewing, I would appreciate it.

Saludos y gracias