P08 Trigger Problem

[kmichaels90]

Seems very odd. If you have the gun cocked with it assembled then remove the upper will it release the firing pin when pressure is applied to the sear bar? If not I would say the issue is with the sear bar or firing pin. If it does release I would think the problem is in the trigger/sideplate/sear bar engagement. That would be an area where I wouldnt know what to do.