spring too long? too many washers in front of/behind the spring?
I seem to remember an issue with an airsporter once that was allowing too much play on the cocking lever producing these symptoms........ and I have seen old airsporters with a few mm ground off the front of the trigger guard to allow extra stroke as well. look for ovalled holes in the linkage, (it seems to be coming back to me now!)
"But we have our own dream and our own task. We are with Europe, but not of it. We are linked, but not comprised. We are interested and associated, but not absorbed."
Winston Churchill 1930