Blocked fan.

Unblock the fan. Ensure that the fan can turn freely (reference 3 of image).

Damaged wire.

Remove the large dust filter from the projector and check if the wire of the left fan of the SMPS compartment is not damaged. Repair if possible, otherwise replace with new one.

Note: SMPS fan 1 is the fan which wire is marked with a brown cable tie (reference 1 of image). SMPS fan 2 is the fan which wire is marked with a red cable tie (reference 2 of image).

Fan end of life.

Replace both fans of the SMPS compartment. See service manual chapter "Replacing the fans of the SMPS compartment".

Note: If one fan of the SMPS compartment is end of life the other fan will probably also (nearly) end of live. For that, it's better to replace both fans at once.

Malfunction Cinema Controller.

Replace the Cinema Control board. See service manual chapter "Replacement of the Cinema Controller".