LG fridge/freezer model no: GR-B206GTQA – Error Code ER CF

Hi,
I have an LG side by side fridge/freezer model no: GR-B206GTQA that I have recently purchased second hand. When I plug the unit in it runs ok for approximately 10 minutes and then the condenser fan stops and then an error code ER CF is shown on the display. The code indicates a problem with the fan. I have cleaned the condenser fan and coils etc as this area was thick with dust and fluff and I have replaced the fan motor with a new one which is the correct motor for this model but nothing has changed. When plugged in the compressor runs fine (no clicking) the coils heat up and the fridge/freezer cools but the fan will only run for approximately 10 mins. When the fan stops (this is when the error ER CF appears) the compressor continues to run and I have noticed that the edge of the divide between the fridge and freezer section gets hot. I had also noticed that the bottom of the evaporator cover inside the freezer looked a little warped/melted, I removed the cover to find that some of the fins on the evaporator had been damaged/bent, I have done my best to separate and straighten the fins so although these are now not touching each other they are still out of shape. Could this damage in any way be associated with the fan not working as it should? I was thinking that perhaps the temperature sensor could be damaged or may have overheated. If this is the case would I need a sensor specific to this model or could I use any LG freezer sensor? I should also mention that if I turn off the fridge and leave it for only several minutes the fan doesn’t come on at all but if the fridge is left unplugged for several hours the fan will run but only for approximately 10 minutes before stopping and the error message is displayed.

I cannot find a suitable solution online anywhere and would be very grateful to anyone who can help me.

Many Thanks
Lee Hardy