Basically as the title says.

I've had this car since April, and this issue would occasionally happen while driving, but never repeatedly. But, since last week, the Columbus head unit has just not worked properly and is turning off and on repeatedly, often with an accompanying electrical popping noise (like when you plug an aux cable from a hi-fi amp into a laptop). This popping noise actually happens even when the car is off, but unlocked. 

Here is a link to a video of the issue that I filmed this morning.

Any advice on repair would be massively appreciated, as I'm trying to avoid a replacement unit due to loving this one (and I reckon the volume controls etc on the steering wheel might not work with a replacement, although I'm not technically savvy so I could be wrong)

there are a lot of old threads for other models talking about problems with the Columbus head unit. They generally end up talking about an issue that causes the unit to get into a "bootloop" - trying to start up and failing over and over (about every 25 secs) - you can hear the hard drive spin up then - nothing. In my case (Yeti L&K, 4wd, 2014 TDi 140) the screen displays the Skoda Navigation splash, but never gets beyond this - but it varies case to case. There are a number of key combinations you can try to "hard reset" the unit (equivalent to turning it off and on again for a PC). None of them worked for me, but pressing the eject and mic button (top right of the unit) and SETUP causes the following to appear over the splash screen: "The system is not able to start up" and "please insert SWL-CD." (see attached) I have not got any further yet as I can't find anyone who has this file yet. I suggest you try this key press combo and see what happens, and if you get the same message search for the SWL-CD file. I'll let you know if I get to it first