Fan pins sporadically stop responding to commands

Weird issue here I'm having trouble pinning down. All of my PWM fan ports on both the duet wifi and the duex expansion board occasionally stop responding to commands. The only way to regain control is to cycle the power to the board. The frequency of occurrence is something like once every two weeks. Still, I'm using some of the fan outputs to control DC motors and solenoids and such so it's a big problem and a bit of a safety hazard for my process when they stop responding to commands halfway through an operation. I did an M122 last time this happened which is shown below:

9:20:54 AMM122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 2.0(RTOS) running on Duet WiFi 1.02 or later + DueX5
Board ID: 08DGM-9T6BU-FG3SN-6J9F0-3S06T-9AY7F
Used output buffers: 1 of 20 (12 max)
=== RTOS ===
Static ram: 28380
Dynamic ram: 96884 of which 0 recycled
Exception stack ram used: 364
Never used ram: 5444
Task NETWORK ready, free stack 324
Task HEAT blocked, free stack 1200
Task MAIN running, free stack 3560
=== Platform ===
Last reset 24:23:25 ago, cause: power up
Last software reset at 2018-11-15 18:25, reason: User, spinning module GCodes, available RAM 5412 bytes (slot 1)
Software reset code 0x0003 HFSR 0x00000000, CFSR 0x00000000, ICSR 0x0441f000, BFAR 0xe000ed38, SP 0xffffffff
Error status: 0
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest block write time: 0.0ms
MCU temperature: min 30.0, current 34.2, max 35.2
Supply voltage: min 24.0, current 24.2, max 24.3, under voltage events: 0, over voltage events: 0
Driver 0: standstill, SG min/max 0/1023
Driver 1: standstill, SG min/max 0/336
Driver 2: standstill, SG min/max 93/585
Driver 3: standstill, SG min/max not available
Driver 4: standstill, SG min/max not available
Driver 5: standstill, SG min/max not available
Driver 6: standstill, SG min/max not available
Driver 7: standstill, SG min/max not available
Driver 8: standstill, SG min/max not available
Driver 9: standstill, SG min/max not available
Expansion motor(s) stall indication: no
Date/time: 2018-12-04 09:20:49
Slowest loop: 192.69ms; fastest: 0.07ms
=== Move ===
Hiccups: 0, StepErrors: 0, LaErrors: 0, FreeDm: 240, MinFreeDm 238, MaxWait: 2545036534ms, Underruns: 0, 0
Scheduled moves: 0, completed moves: 0
Bed compensation in use: none
Bed probe heights: 0.000 0.000 0.000 0.000 0.000
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1
=== GCodes ===
Segments left: 0
Stack records: 1 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 idle 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 ===
Slowest loop: 167.86ms; fastest: 0.01ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0) Telnet(0)
HTTP sessions: 1 of 8
- WiFi -
Network state is running
WiFi module is connected to access point
Failed messages: pending 0, notready 0, noresp 0
WiFi firmware version 1.21
WiFi MAC address 84:f3:eb:83:49:94
WiFi Vcc 3.41, reset reason Turned on by main processor
WiFi flash size 4194304, free heap 15824
WiFi IP address 192.168.12.64
WiFi signal strength -57dBm, reconnections 0, sleep mode modem
Socket states: 0 0 0 0 0 0 0 0
=== Expansion ===
DueX I2C errors 66389

The problem with the fans on the DueX5 is explained by the very large I2C error count. The usual cause of these I2C errors is a poor ground connection between the VIN- terminals of the Duet and the DueX5. See [duet3d.dozuki.com] for wiring recommendations.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thank you dc42. I didn't have proper ferrules on the duex as i had run out of stock. After seeing your response I went back and installed the ferrules and haven't had the problem since. Will let you know if it pops back up but I doubt it will.

It appears I spoke too soon! The PWM fans all just turned ON and stopped responding to commands to turn it off again. Below is another M122 report. Is there anything else I can check? Another clue may be that when this happens the duet also won't respond to hitting the emergency stop button on the web interface. If I physically cut the power, however, it acts normal again after I turn it back on.

M122
=== Diagnostics ===
RepRapFirmware for Duet 2 WiFi/Ethernet version 2.0(RTOS) running on Duet WiFi 1.02 or later + DueX5
Board ID: 08DGM-9T6BU-FG3SN-6J9F0-3S06T-9AY7F
Used output buffers: 1 of 20 (15 max)
=== RTOS ===
Static ram: 28380
Dynamic ram: 96884 of which 0 recycled
Exception stack ram used: 388
Never used ram: 5420
Task NETWORK ready, free stack 324
Task HEAT blocked, free stack 1176
Task MAIN running, free stack 3560
=== Platform ===
Last reset 102:43:11 ago, cause: power up
Last software reset at 2018-11-15 18:25, reason: User, spinning module GCodes, available RAM 5412 bytes (slot 1)
Software reset code 0x0003 HFSR 0x00000000, CFSR 0x00000000, ICSR 0x0441f000, BFAR 0xe000ed38, SP 0xffffffff
Error status: 0
Free file entries: 10
SD card 0 detected, interface speed: 20.0MBytes/sec
SD card longest block write time: 0.0ms
MCU temperature: min 31.5, current 34.1, max 34.9
Supply voltage: min 24.0, current 24.2, max 24.3, under voltage events: 0, over voltage events: 0
Driver 0: standstill, SG min/max 0/308
Driver 1: standstill, SG min/max 0/1023
Driver 2: standstill, SG min/max 55/701
Driver 3: standstill, SG min/max not available
Driver 4: standstill, SG min/max not available
Driver 5: standstill, SG min/max not available
Driver 6: standstill, SG min/max not available
Driver 7: standstill, SG min/max not available
Driver 8: standstill, SG min/max not available
Driver 9: standstill, SG min/max not available
Expansion motor(s) stall indication: no
Date/time: 2018-12-17 17:47:39
Slowest loop: 185.15ms; fastest: 0.08ms
=== Move ===
Hiccups: 0, StepErrors: 0, LaErrors: 0, FreeDm: 240, MinFreeDm 238, MaxWait: 325248147ms, Underruns: 0, 0
Scheduled moves: 0, completed moves: 0
Bed compensation in use: none
Bed probe heights: 0.000 0.000 0.000 0.000 0.000
=== Heat ===
Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1
=== GCodes ===
Segments left: 0
Stack records: 1 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 idle 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 ===
Slowest loop: 167.72ms; fastest: 0.01ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0) Telnet(0)
HTTP sessions: 1 of 8
- WiFi -
Network state is running
WiFi module is providing access point
Failed messages: pending 170, notready 0, noresp 0
WiFi firmware version 1.21
WiFi MAC address 86:f3:eb:83:49:94
WiFi Vcc 3.41, reset reason Turned on by main processor
WiFi flash size 4194304, free heap 14672
WiFi IP address 192.168.42.14
Connected clients 2
Socket states: 0 0 0 0 0 0 0 0
=== Expansion ===
DueX I2C errors 4078

Please can you post photos showing how you have the Duet and DueX connected together. Also I suggest you upgrade the firmware to 2.01 or 2.02RC6.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Ok. I'll run the update today. In the meantime here are a few images.

Looks like you have separate ground wires going from each of the Duet and DueX5 to the PSU. The wiring instructions on the wiki say specifically that you should not do that.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].