Following up on the previous and some interesting observations,
Firstly, huge thank you to MDAR for your help and patience
Right new 4DC module shipped to me and installed, config copied and works flawlessly.
The GP4, I’m still intrigued how you managed to bring it back to life but I can confirm it is working.
So, the interesting observation is that the system has previously been connected to using the VMB1USB. I swapped this out with the VMBRSUSB due to it being din mounted (unfortunately the usb connector is in the wrong orientation, why have it coming out the front when down, sideways or rear connected would be far better if mounted in a cabinet??) and the previous query of the VMB1 being faulty.
The previously failed FW updates due to “The integrity of the firmware could not be verified” did not occur and the units updated without issue - and seemingly quicker too.
Out of curiosity, I reconnected the previously ‘dead’ 4DC and attempted the FW update and would you believe it, it worked without hesitation!
I’m extremely grateful for the support and the rapid shipping of the replacement module (which you can now have back ) I’m also shipping the VMB1 back so you can assess the potential issue.