I agree that you should replace the back though I would always swap inserts with my system (had a couple of handy little Bronica insert holders that attached to a belt, so I assume Bronica meant for the inserts to be interchangeable) and never had any problems. Buying a new back is not usually much more than buying an insert so see what you can find out there.

Don't throw out the old back - it's fun to open up and experiment on 'junk' like this so that you'll have a better idea of what to do in the future if something new goes wrong.