Update regarding our Vent Axia Kinetic Plus B R/H.
Worth checking the condition of the fans.
Installed 6 years ago, cleaned the filters and checked the summer bypass, louvres stuck in open position.
Have screwed the louvres in the closed position for now and disconnected the actuator.
Fan covered in thick mould.
Not difficult but front, back and side panel need to be removed. Then fan.
All bearings fine.