It is a reset:M122 B122
Diagnostics for board 122:
Duet TOOL1LC firmware version 3.2-beta4.1 (2020-12-03)
Bootloader ID: not available
Never used RAM 4580, free system stack 96 words
HEAT 50 CanAsync 89 CanRecv 83 TMC 60 MAIN 326 AIN 64
Last reset 00:00:19 ago, cause: software
Last software reset at 2020-12-03 10:17, reason: HardFault, available RAM 4360, slot 1
Software reset code 0x0060 ICSR 0x00417003 SP 0x200011c0 Task
Stack: 20001014 00000012 0001d3e3 00000000 20000928 0001757d 000184fe 01000000 0000aed0 0000afca 20001210 200032d8 00000020 00017d11 20004668 00000000 20001300 000086e5 0000aed0 20004678 0000afca 41a73180 a5a5a5a5 a5a5a5a5 a5a5a5a5 a5a5a5a5 a5a5a5a5
Driver 0: position 0, 80.0 steps/mm, standstill, SG min/max 0/0, read errors 0, write errors 1, ifcnt 36, reads 9946, writes 9, timeouts 0, DMA errors 0
Moves scheduled 0, completed 0, in progress 0, hiccups 0
No step interrupt scheduled
VIN: 12.3V
MCU temperature: min 28.7C, current 28.9C, max 28.9C
Ticks since heat task active 197, ADC conversions started 19940, completed 19940, timed out 0
Last sensors broadcast 0x00000000 found 0 201 ticks ago, loop time 0
CAN messages queued 99, send timeouts 0, received 189, lost 0, free buffers 36
But I am in beta 4.1 and it happen with both heater off. Only when I reset the board via the dialogue box that appear then we save the config.g file