Did the A. Lange & Sohne wristwatch company ever have any ties to the Nazi
Party or ever use slave labor? And why did Russia bomb the Glashutte
factories where they made the watches?

All German industry during the Nazi regime had 'ties' with the Nazi
Party, like it or not.

Don't know about the use of slave labour.

Bombing was not that accurate during the Forties (or even today!) and
the Soviets may not have been targetting those particular factories.

Possibly, they just dropped their bombs willy nilly on any factory.