miele/liebherr fridge freezer

Our Miele fridge freezer (KFN12823SD) made by Liebherr went wrong a week ago. The freezer stopped cooling and temperature increased until warning light and buzzer went off. If switched off at the mains, left off for some time (say an hour), and then switched on again the freezer would cool for approx 30 – 40 minutes and then stop cooling. If just left it would not switch onto cooling again but had to be turned off at the mains switch and left for say an hour before switching on again when it would again cool for perhaps 30 – 45 mins. I’ve currently got the fridge freezer on a timer so that it is on for 45mins and then off for 2 1/4 hours continuously ie on 8x in a day. The fridge compartment is operating as a ‘larder’ averaging 8 – 9 C. The freezer compartment is not in use. We have a chest freezer so for the moment can operate like this. An additional factor is that 3 years ago the compressor was replaced with an Embraco EM X80CLT unit by a specialist repairer. Anyone have any thoughts about this fault. I suppose it could be the compressor but it has been working as described above for some days now – I would have expected a failing compressor to completely fail by now.
I have thought about feeding power to the compressor directly via a temperature (cooling) controlled switch I have but I don’t know what needs to be fed into the box directly attached to the compressor besides a 250v mains feed – it seems to have 4 wires going into the box plus possibly a grounded earth. Any ideas very welcome.
Thanks
Peter