Wilwood or aftermarket Master cylinder that works with kelsey Hayes Calipers?

IDK, maybe your brake push rod is not straight causing an uneven push on the piston resulting in leakage. Maybe you just got a hold of a few bad ones? My first Duster had the K H with the stock MC. never leaked. I had it 24 years. the one I have now has a stock MC for K H but I have the Wilwood set up. It does not leak. I suspect something is out of allinement.