@droftarts
Thanks for responding!
To answer your questions in order:
Was the M569.5 command generated by the Closed Loop plugin?
Yes
Are you running in standalone or SBC mode?
Standalone
Is the SD card good (it could be the SD card can't cope with the speed at which the data is collected and written)?
Not entirely sure how to qualify an SD card for this? It is a 16GB SanDisk Ultra micro SD (I believe the stock card that came with the board but not 100% certain of that). It has been reformatted to eliminate the partition that the stock micro SD cards that come with the boards have.
Can you send M122 B# (where # is the CAN address of the 1HCL board) when the printer restarts, which may show the reason for the crash?
M122 Prior to reconnection
M122 Before Reset.png
M122 After Reconnection
M122 After Reset.png