Maybe the tungsten wire is broken or loose. Try removing the battery and see if that get the mirror down. If that’s the case, the wire is broken or loose. To see it you have to remove the top cover. That wire links the speed dial to another spring control placed below the rewind lever mechanism. When the wire is loose or broken, the spring sets the speed to infinity until you reset the signal by removing the battery. Hope that helps.

There’s a wire inside the top cover. It links the speed dial with another dial and a spring located in the left side under the rewind lever. It it’s either broken or loose (spring tension is lost or it went out from the pulleys) the speed will always go to infinity and the mirror wont come down until reseting the signal. You have to replace the wire if broken or set it tight again if its loose.