Ruger 22/45 sear engagement question

[Tank.45]

So i just finished putting in a home made pre travel stop in my ruger Mk III 22/45. After testing function with the gun assembled, i noticed the hammer is not catching on the sear or it is falling as the bolt slides forward. This is only happening once every 20-30 dry fires and is not repeatable by anything i can determine. I made sure there is still some take up so that there is not any pressure on the sear until you have started moving the trigger slightly. When i had the receiver and the frame apart the sear engagement looked fine and was grabbing the hammer every time. I made absolutely no mods to the engagement surfaces on the sear or hammer.

My thoughts:

The only thing i can think of is when i put receiver back on the frame, the receiver pushes down or exerts some force on the connector and is causing the sear to engage less than with the receiver off.

If anyone could give me some input that would be much appreciated

Thanks

[SW911]

Might want to ask at rimfirecentral.com
They have a subforum specifically for the 22/45.