Walker mower blades collide - what?

The blades on my 2-blade Walker Mower collide after I hit a blackberry root (I think). What is the problem and how do I repair it.

If you have the two gear boxes sitting on top of the deck, they have to be timed with the blades 90 degrees from each other. You may be able to take one blade off and turn it to the correct configuration, but that will be temporary due to the worn gears in the box that will jump teeth again.