Hi Colin, saw your post this morning and would like to offer my opinion, for what it's worth, although I have not been part of this thread previously.
I am assuming your unit is a "CBE-DS-520" which is the distribution/consumer unit which supplies the various 12 volt circuits in your motorhome. Depending on the model, there are a number of different types as they are customised by the motorhome manufacturers to their individual specifications, the fuse for the fridge tends to move position. However, it is mostly in position 6 and is a 30 amp fuse.
I would suggest that you check here first making sure that the fuse holder is OK as a lot of heat can be generated by the load from the fridge. This can cause the fuse holder to lose tensile strength and result in a bad connection and cause the fridge to operate intermittently
If all is OK here then check for 12 volt supply, at the fridge, when engine running. If there is no supply voltage then things are now going to become a little more involved. i.e. you will now need to dig deeper into the DS unit and check the internal connections. If you have your motorhome from new you should have a schematic wiring diagram for your 12 volt system.
There are a number of plugs/sockets inside the unit and, from memory, the + (positive supply) for the fridge comes through plug number 22 which is coloured RED. The fridge supply will be on pin 2 or 3. The plug has a RIDGE on one corner and if you look at it with that ridge at top left, then pin 1 is the top left corner with 2 and 3 vertically below.
Plug number 27 which is white, and is the largest plug there (12 connections) carries all the negative connections. It would be a good idea to disconnect both of these plugs, 22 and 27, and check the pins, in both plug and socket, for signs of overheating.
That should be enough for you to check, for the moment, and hopefully you will find the problem. Otherwise, it gets a little more complicated from here. Come back if you don't get it sorted.