When I originally bought my Auster it had an impeccable history on the leakdown tests - all around 78/80. However, I got an annual done before I took delivery and one cylinder had dropped to 37/80 - the aircraft had not been flown much in the previous year. Turned out to be corrosion in one valve cause by sitting - as well as a loose valve seat. The history of leakdown tests is just that - history - what it is now is what matters. We got the cylinder done immediately and has been perfect since.
I know its not a Jab motor but these things happen in all