Liebherr ICUS 3314 integrated Fridge/Freezer wont stay cold?

Liebherr ICUS 3314 Index 20/001
Serial #30.608.524.4
Service# 9989628-00
Approx 2013/14 purchase new

For the last 10 days the fridge will not stay cold. The temp display will show 4c, however its warm inside the fridge. We’ve moved everything outside to our old Bosch classic in the garage.
We’ve tried the manual defrost of the freezer, turned it off and on again, lowering the temp down to 1c and using super frost, which I do appreciate is a freezer function, to try and shake it out. Sometimes ice will form on the rear wall of the fridge, but it doesn’t last more than an hour or so. The drain hole is not blocked.
It will get cooler, but a cheap amazon fridge thermometer shows it won’t go below 8 or 9c despite what’s on the display.

So we’re 10 days in now, there’s not much help on the Liebherr website, so I thought I’d ask here !

1. Are there any suggestions what we could do next?
2. Any recommendations for a repair contact (Solihull)?
3. Should we repair or just replace?

Something of a Liebherr sceptic, we were recommended an integrated fridge-freezer from Liebherr by John Lewis 10 years go when we replaced the kitchen. The first one did not work well at all, and was replaced by Liebherr under warranty with this one in late 2013/14. This one has been very very noisy at times, and requires monthly manual defrost, but has otherwise been reliable.

Thanks in advance for your help.
Robert