Whirlpool S20D TSB33 – Fridge Getting Colder and Colder

We have a Whirlpool S20D TSB33 which is about 7 years old.

The other day I noticed the fridge was a bit colder than normal and looked at the control panel and saw “–” on the FRIDGE side of the display. None of the other icons are on (holiday / party etc).

Since then it’s been steadily getting colder and colder, to the point where it’s starting to freeze some of the food in there and we’ve had to start switching it off for periods to let it warm up a bit.

I’ve tried switching it off for at least 2 minutes but it just comes back with either the double dashes or sometimes with a blank where the temperature should be.

It occasionally shows error code “d” but this apparently means faulty baffle, which should result in a fridge not cooling? Or could it mean the baffle is stuck on?

The double dash display lead me to find a lot of discussion about a common fault with the rear board, but in those cases the double dash is on the freezer side of the display. Over the last few months, I’ve noticed a constant clicking coming from behind the fridge, but I just thought a fan was catching a bit. But maybe this means we do have the rear board problem.

Any advice on way to proceed? Should I try changing the back board because of the clicking and hope this might also fix the problem? Should I take more notice of the “d” message even though it doesn’t seem to match the symptoms? Could it be a front-board problem (they seem more expensive to replace)?

Thanks in advance for any help!