Thanks for your reply.
Is what I was doing without success (actually I used to press enter instead of clicking on the send button).
Nevertheless I've tried again and this time the M122 worked.
This is what it have reported:
6:02:09 PM
M122
Resume-after-power-fail state saved
Printing paused
Printing resumed
=== Diagnostics ===
Used output buffers: 6 of 32 (16 max)
=== Platform ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 1.21 running on Duet Ethernet 1.02 or later
Board ID: 08DDM-9FAM2-LW4S8-6J9FJ-3S86S-TJY7W
Static ram used: 16152
Dynamic ram used: 100336
Recycled dynamic ram: 2296
Stack ram used: 1224 current, 7792 maximum
Never used ram: 4496
Last reset 08:11:41 ago, cause: power up
Last software reset at 2018-03-31 23:19, reason: User, spinning module GCodes, available RAM 7760 bytes (slot 0)
Software reset code 0x0003 HFSR 0x00000000, CFSR 0x00000000, ICSR 0x0441f000, BFAR 0xe000ed38, SP 0xffffffff
Error status: 8
Free file entries: 9
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest block write time: 12.8ms
MCU temperature: min 33.9, current 35.5, max 36.1
Supply voltage: min 23.9, current 24.1, max 24.2, under voltage events: 0, over voltage events: 0
Driver 0: ok, SG min/max 0/1023
Driver 1: ok, SG min/max 0/339
Driver 2: ok, SG min/max 0/348
Driver 3: ok, SG min/max 0/1023
Driver 4: standstill, SG min/max not available
Date/time: 2018-04-01 18:01:28
Slowest main loop (seconds): 0.041106; fastest: 0.000050
=== Move ===
MaxReps: 5, StepErrors: 0, LaErrors: 0, FreeDm: 120, MinFreeDm 120, MaxWait: 2ms, Underruns: 0, 0
Scheduled moves: 638529, completed moves: 638500
Bed compensation in use: mesh
Bed probe heights: -6.933 -6.174 -4.739 -4.343 -5.052
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1
Heater 0 is on, I-accum = 0.0
Heater 1 is on, I-accum = 0.4
=== GCodes ===
Segments left: 1
Stack records: 2 allocated, 0 in use
Movement lock held by null
http is idle in state(s) 0
telnet is idle in state(s) 0
file is doing "G1 X35.022 Y27.291 E0.02095" in state(s) 0
serial is idle in state(s) 0
aux is idle in state(s) 0
daemon is idle in state(s) 0
queue is idle in state(s) 0
autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Responder states: HTTP(1) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0) Telnet(0)
HTTP sessions: 3 of 8
=== Network ===
State: 5
HTTP sessions: 3 of 8
=== Expansion ===
According to diagnostic info there wasn't any power issue event so I cannot understand the reason why the printer has paused just a couple of minutes ago.
I noticed that on diagnostic is wrote "Error status = 8". Can it be useful? What is its mean?
5:59:05 PM
Resume-after-power-fail state saved
Printing paused
Printing resumed
5:53:53 PM
Resume-after-power-fail state saved
Printing paused
5:53:51 PM
Resume-after-power-fail state saved
2:55:32 PM
M122
69 points probed, mean error 0.072, deviation 0.072
Height map saved to file heightmap.csv
File MYLM_motor-holder.gcode selected for printing
Resume-after-power-fail state saved
I'm using Cura 1.2.3 under CentOS 7 for slicing. Could the slicer causes a unexpectable behavior of duet?
Other ideas?