Sear engagement issue it sounds like. More specifically insufficient overlap.
Here is how to adjust it yourself if you have a bit of technical inclination...
NB: Usually the Sear is set at the factory and doesn't need adjusting.
Symptoms of incorrect sear adjustment.
Too much sear adjustment: Trigger feels 'creepy'.
Too little sear adjustment - trigger does not engage, or trips as you cock the air pistol (as in this case).
Tools required:
Standard 162 Tool Box worth of Allen Keys
1.27mm Allen Key
Fig.1: One Morini 162MI - Long Barrel, Long Sight Radius. Beautiful grain in the grip. Also: not working.
Fig.2: Grip removed - about to remove the trigger unit forward bolt - biggest and baddest Allen key in the set used.
Fig.3: Bolt removed.
Fig.4: Half cock the pistol will reveal the pin to be removed to free the trigger unit.
Fig.5: An appropriately sized punch and mallet so as to not damage the finish.
Fig.6: Trigger unit removed.
Fig.7: Grub screw in the top of the trigger unit being adjusted with 1.27mm Allen Key.
Brief instructions:
1) Turn the Allen Key CCW until the sear catches. You can cock the unit by pulling the cocking arm down. If it stays down you're golden.
2) Turn the Allen Key CW until the sear drops.
3) Turn the key back ~ 1/16 of a turn CCW from the sear disengagement point.
4) Test to ensure reliability of sear engagement.
Sear Adjustment: Clockwise - less overlap. CCW - more overlap.
I also held by thumb over the hammer pin so as to cushion it as the sear dropped. Unsure if necessary, but I felt better about not damaging the unit.
Fig.8: Assembly is the opposite of disassembly. Do not over-torque bolt; snug will do.
