Zurn AquaFlush

I had a service call yesterday at a church that I have been servicing for several years. I thought I was going to do a simple rebuild of a Zurn AquaFlush valve on the toilet. After rebuilding the valve, I have water coming out of the vacuum breaker at the end of every flush. I have been in the plumbing industry for over 16 years and have never ran into this problem. Anyone know a solution for me?

Did you try replacing all the parts again? Maybe, something got a small crack in it.

Nope, but I did inspect the valve for cracks. I have seen some strange things if the cap has a crack. I hated to through more money at this thing. I do a lot of things for them for free as long as I don't have to put much into it. I'll bite the bullet and see if that works. Thanks!