5D3 reboot loop with new iMac Pro

Having issues with my 5D3 when connected to brand new iMac Pro. Closes down, but reboots after around 15 seconds. Connectivity is via USB-C. Unit works as it should with 27" Retina iMac, so it seems to be a compatibility issue with the new iMac Pro. Apple have been extremely helpful in testing and the fault appears to be with the Drobo. Drobo support state they have been able to replicate the fault, but I’m getting no where with any updates from them, which is extremely frustrating.