Breaking a 1/4" router bit usually takes a lot of force, which can knock the Z assembly out of alignment depending on how rigid it was built. It may or may not bind, and it may just not be a true 90 degrees to the table top if you had it set that way before the cutter snapped.
I did that in the past and a few love taps with a dead blow hammer put it back into proper vertical alignment. I had no binding before or after the bit broke though. I tightened the bolts more to help keep them from shifting on impact.
CarveOne
CarveOne
http://www.carveonecncwoodcraft.com