Welcome to the wonderful world of parts made to the exacting specification of "somewhere close"!
I'll try to explain what may be going on the best I can.
Here is the pre-2005 factory trigger. I don't have one of the RB, but they work the same.
The blue is the safety lug on the trigger.
The surface of the safety lever marked red is the surface that contacts the lug in the safe position.
The surface marked in yellow is the area the lug must be able to clear and travel to fire and move far enough to contact and force the sear down enough to remove the bolt. That is accomplished via the WOP spring contacting the shoulder on the sear visible to the right of the lug on the trigger. When you slowly pull the trigger all the way back you'll feel the initial resistance of the WOP/trigger reset spring then the resistance of the sear reset spring as it depresses the sear.
Clear as mud yet?
If you remove the bolt look in the bolt handle cut in the receiver as you pull the trigger. You will see or should see the sear move down to or slightly below the bolt race.
Just as a guess without having the club on the bench to see whats taking place I'd say the "yellow" surface is preventing the lug from moving its full length of travel and not allowing the trigger to force the sear down enough or something is preventing the sear from dropping all the way, enough to fire, but not enough to release the bolt. In the case of the lug clearance to the yellow surface a little more clearance is better than not enough.
If in fact its a clearance issue, "carefully " using a file or Dremel remove a small amount, a few thousandths then try it, remove a bit more, try it and etc.
If its a sear travel problem then you need to disassemble it and find whats causing it, dirt, crud, misplaced crowbar ....
Either way its an easy fix.
Oh, the "somewhere close" parts? The safety lever is stamped steel, so its not of the ordinary for the dimensions to vary slightly between parts, so I doubt the the RB trigger is causing you grief. I've installed a dozen or so, a mix of both the MAR-1 and MAR-2 triggers. Mostly I run into safety engagement issues.
The short explanation!