Jeff,
Despite what you may have heard about 'resetting' the chrono hand with a magic combination of buttons/crown - this can't be done with this movement. (Maybe it can be done with modern quartz's, I don't know)
Either the hand is slipping or the movement needs looking at. If the chrono hand tube is loose, you may need a new hand, which is problematic, as they are very hard to find. I had a similar problem, took ages o sort out a hand. Either way, you'll need to have a watchmaker look at it.

Stewart
- Heuerville