RRF 3.3RC1+1 - Adding axis to M956 causes system reset

OwenD

Board: Duet 2 WiFi (2WiFi)
Firmware: RepRapFirmware for Duet 2 WiFi/Ethernet 3.3RC1+1 (2021-05-01)
Duet WiFi Server Version: 1.26
Duet Web Control 3.3.0-rc1

I've noticed that adding any axis command to M956 causes the system to restart.
This was not present in 3.3b3

This works

M956 P0 S1000 A0

This crashes

M956 P0 X S1000 A0

M122

M122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 3.3RC1+1 (2021-05-01 21:43:27) running on Duet WiFi 1.02 or later
Board ID: 08DGM-917NK-F2MS4-7J1DA-3S86T-TZTWD
Used output buffers: 3 of 24 (24 max)
=== RTOS ===
Static ram: 23876
Dynamic ram: 78048 of which 0 recycled
Never used RAM 9636, free system stack 182 words
Tasks: NETWORK(ready,11.6%,205) ACCEL(notifyWait,0.0%,334) HEAT(delaying,0.0%,330) Move(notifyWait,0.1%,364) MAIN(running,87.9%,405) IDLE(ready,0.3%,29), total 100.0%
Owned mutexes: WiFi(NETWORK)
=== Platform ===
Last reset 00:01:58 ago, cause: software
Last software reset at 2021-05-02 11:31, reason: HeatTaskStuck, Platform spinning, available RAM 9396, slot 0
Software reset code 0x4140 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0041f80f BFAR 0xe000ed38 SP 0x2001290c Task ACCE Freestk 318 ok
Stack: 004339f1 004339f2 610d0000 00000000 40f86a00 41bb0a4a 3edb6dbf 3331bb4c 40000000 b5dde7a3 388ab355 bb360b61 3e2aaaab 3f800000 3f800000 42040000 4354c416 00000000 00000000 00000000 200122c8 00000001 200122c8 ffffffe8 00000006 00000004 20004c7c
Error status: 0x04
Aux0 errors 0,0,0
Step timer max interval 0
MCU temperature: min 22.9, current 23.4, max 23.9
Supply voltage: min 24.2, current 24.3, max 24.5, under voltage events: 0, over voltage events: 0, power good: yes
Heap OK, handles allocated/used 99/9, heap memory allocated/used/recyclable 2048/332/208, gc cycles 0
Driver 0: position 0, standstill, SG min/max not available
Driver 1: position 0, standstill, SG min/max not available
Driver 2: position 0, standstill, SG min/max not available
Driver 3: position 0, standstill, SG min/max not available
Driver 4: position 0, standstill, SG min/max not available
Driver 5: position 0
Driver 6: position 0
Driver 7: position 0
Driver 8: position 0
Driver 9: position 0
Driver 10: position 0
Driver 11: position 0
Date/time: 2021-05-02 11:33:44
Cache data hit count 4000074970
Slowest loop: 15.66ms; fastest: 0.18ms
I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
=== Storage ===
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest read time 1.2ms, write time 0.0ms, max retries 0
=== Move ===
DMs created 83, maxWait 0ms, bed compensation in use: none, comp offset 0.000
=== MainDDARing ===
Scheduled moves 0, completed moves 0, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== AuxDDARing ===
Scheduled moves 0, completed moves 0, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
Heater 1 is on, I-accum = 0.0
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
Telnet is idle in state(s) 0
File is idle in state(s) 0
USB is idle in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
Daemon is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty.
=== Filament sensors ===
Extruder 0 sensor: ok
=== Network ===
Slowest loop: 82.21ms; fastest: 0.00ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions
HTTP sessions: 1 of 8
- WiFi -
Network state is active
WiFi module is connected to access point 
Failed messages: pending 0, notready 0, noresp 0
WiFi firmware version 1.26
WiFi MAC address bc:dd:c2:89:a0:bb
WiFi Vcc 3.38, reset reason Power up
WiFi flash size 4194304, free heap 23856
WiFi IP address 192.168.1.163
WiFi signal strength -60dBm, mode 802.11n, reconnections 0, sleep mode modem
Clock register 00002002
Socket states: 0 0 0 0 0 0 0 0

OwenD

Scratch that.
Rolled back to 3.3b3 and it's still crashing.
Will look into it some more and come back.

OwenD

Hmmm.
Some sort of weird memory thing going on I think.
Did a full power off restart and it started working with 3.3b3
Updated to 3.3RC1 (with power off restart) and it's fine.
Updated to 3.3RC1+1 (with power off restart) and it's fine.

Sorry for the false alarm.
I'll leave this here in case anyone else has similar issues.