Siemens KA58NA04GB/09 Stops freezing

Hi, very new here and very confused.
I have a Siemens American Style Fridge Freezer. (Ok it's really a rebadged Daewoo)

The bottom of the freezer freeze, but the system seems to stop circulating air. (i.e. the fan stops)

So I've tested the Fan Motors and they are ok
I tested the Sensors and they are all operational
I've tested the Thermal fuses (cut-outs if you prefer) and they are fine too.

I've checked the power to the fan motors and they get 13V or near enough for around 2 hours or more. Then after making Ice once or twice the fans stop and won't restart. The defrost doesn't seem to kick in and It starts to frost-up. The Fridge side starts to warm because none of the fans are working.

Oddly, I made a mistake when testing and shorted pins 1 and 9 on connector CN11. This appears to be the I-Sensor.
Prior to the short the motherboard was not delivering power to any fan, but after the short off they went happy as larry.

Also the motherboard is new, the defrost unit is new. and to reiterate I reckon all sensors are working. And fan motors have been bench tested.

Any ideas anyone?