When exactly does this occur? If it's running on full load (For example while mining) and the fan stops working, it could end badly for your GPU. Do you have any monitoring software installed? If not, try using MSI Afterburner, set the fans to Auto, check if it happens again, could be an issue with the drivers perhaps?

Since it's a new GPU, you could also send an email to the manufacturer, it's possible that the fan's pins (They control the fan's spinning speed) are not working as they should.