Hi @adamdove
If the compressor motor running continually trying to keep the refrigerator cool or is it stopping occasionally for a short while and then starting again i.e. <10 minutes?
There definitely seems to be an issue with the temperature control in the refrigerator and freezer.
It appears that instead of maintaining the temps around -18°C (freezer) and 4°C (refrigerator) as most refrigerators do (your freezer gets very cold at -30°C), by the compressor cycling on and off as required, and then having the temps rise when a defrost cycle occurs (due to the compressor being stopped and the defrost heater being turned on) it appears that it is not cooling at all after a defrost cycle has ended, the compressor has been turned back on again to get to the required temperatures, which once achieved it is then turned off and the next defrost cycle occurs.
It appears that your model has an adaptive defrost cycle in that rather than the cycle occurring in a regular time frame e.g. every 10 hours it looks like it is done on accumulated compressor run time e.g. if the accumulated time was say 10 hours then it might take more than a straight 10 hours to achieve this as it depends on how often the compressor is running and for how long each time i.e. usually it runs less often and for shorter time intervals overnight than during the day as the ambient temp is cooler and the doors aren't opened as often letting in the warmer outside air which has to be cooled down.
The defrost cycle time appears to be OK at ~25 minutes.
Unfortunately I cannot find a service manual for your model so that the diagnostic tests could be conducted to find out exactly what's wrong.
But it seems that it may be a control board issue, but this is just a guess.