10 gauge lifter double firing--both hammers fall

[8GAUGE]

Ok Guys, I know several of you must have dealt with this issue before. My Parker 10 gauge lifter doubles sometimes when I fire it. The trigger pull is about 2 pounds on both hammers! I have had the gun professionally cleaned and locks look brand new with no appreciable wear.

The gun double fires about 40% of the time. I understand that the angle on the sear engagement needs to be changed. Is this the correct way of correcting this issue? I would like to see a normal trigger pull of about 6 pounds like my other double guns have. Any help would be appreciated.

Thanks!