My experience says it is dead
It might be cheaper to replace than repair. Get an estimate first.
I had a camera outfit- paid $85 for it. The lens wouldn't extend all the way. $100 to repair. New camera!
I have 2 M12Vs sitting here on my desk that won't even make good boat anchors. The variable speed components are electronic & are encased in an epoxy block with wires sticking out. Trying to repair is an impossibility. I have found it impossible to get a replacement as they are no longer available.
It is possible to bypass the speed control, but it is hardly worth the effort. The router will then only run at high speed with very little torque.
Your best bet would be to find 1 at an estate sale or garage sale & have enough luck to get it before somebody else who knows what it is worth beats you to it. Another possibility would be one of the internet buy & sell sites. I found one right here in Winnipeg on Kijiji. Another came from the Denver area. Shipping was as much as I paid for the router. One of those crapped out a short while after I got it, so it is a definite crap-shoot,even if you do find one.
As the previous poster said, 'GO BUY SOMETHING ELSE'! Paul