Culligan Mark 59 started continuous flow to drain

[Dandgann]

I just repaired this unit 3 or 4 months ago. Now a new issue has arisen. After a recent recharge cycle there is a constant trickle into the discharge drain (I've had to bypass it to conserve water). Either a valve diaphragm has perforated or some check valve or gasket has given up. I found a good diagram at this URL (http://cassidywater.com/service/Mk2_5_Fr1975.pdf) but I'm not sure just where to look for the problem. Wonder about the function of the eductor. It was obviously worn when I tore the unit down. I tried to nurse it and carefully reassemble it. Of course the next issue will be finding parts. Any advice for either of these issues?
1. What's gone wrong to allow the water leakage?
2. Where can I find parts?

Thanks a lot!