Dell WD19TB Fan failure

I've had my WD19TB dock for around a year, its under warranty until Jan 2024.

I have used it daily since I bought it and have had no complaints, however over the last few months I have noticed the fan has been coming on for longer and running faster than normal.

I know the fan is meant to keep the unit cool but its not under load when this happens, the room is air conditioned and quite cold so I don't think that its an environmental factor or anything to do with the dock being warm/hot (Its cool to the touch and the exhausted air is room temp so its not extracting any heat from the device).

The event that has prompted me to join this community was around 10-15 minutes ago where the fan spun up to full speed and stayed on, its only just stopped now so I'd say it was on solidly for 10 minutes. Now it starts and spins forever.

The dock isn't warm, the room isn't warm, the laptop is not under load.
I have updated to the latest firmware but without any change.

Any ideas? 

I've read that other had this problems and dell support helped to solve this, maybe you can help me too?