Hi, Mike here.
I have a similar rebooting problem, I have a 2015 Superb Estate, my Columbus unit has DAB radio, I can't enter setup mode.
Model number is 3T0 035 686 N , HW: H27 , SW:6276.
Initially I thought the HDD was failing so after using Paul's excellent HDD replacement instructions I found my unit already has a 32Gb PATA SSD drive (Cactus KD32GF-210 FW:0513.)
I connected it to my PC and checked the contents. There are 3 partitions, one of which show up in windows formatted in FAT32. I successfully made an image backup (using Ashampoo Backup Pro) and restored it to an old 80gb disk I had spare. Because it successfully copied I then reassembled the original parts and the fault remains.
One thing I noted is that the fault initially was intermittent but gradually becoming worse, the colder the weather the more likely it would work normally I am waiting for a cold night to see if it bursts into life again. I think my firmware is the latest but not sure, my maps are well out of date (as original installed).
Anyone have any thoughts about the above?
I'm Thinking about buying a refurbished unit with latest maps but no DAB and maybe try fixing mine in the meantime
Thanks in advance, Mike Bush