Is the angle on one side of the hammer cam to allow the bolt leg to slip around it easily when the hammer is falling?
As you pull the hammer back the bolt leg is pushed up by the side of the cam on the hammer, causing the bolt head to drop out of the cylinder stop notch and retract through the frame. As the hammer continues back the bolt leg eventually slips off the side of the cam when it reaches the bevel on the cam - there's no more 'side' of the cam pushing on the bolt leg. That allows the bolt spring to force the bolt head back up through the frame and into the cylinder stop notch. The purpose of the beveled angle on the cam surface is to cause the bolt leg to fall off the side of the cam.
Once the bolt leg has fallen off the side of the cam the only thing holding it up through the frame is the bolt spring; the hammer is no longer involved. When the hammer drops the bolt leg simply slides up the surface of the cam along the bevel and then slips over the edge into place alongside the cam. It's possible there's a burr on the bolt leg or the cam surface that affects that movement, but it would seem to me that it would be a pretty big burr.
I still think the trigger sear is getting snagged by the half cock notch.