Much better angle, thanks - Kevin you'll have to take this with a grain of salt since I am unfamiliar with the internals on that particular model, but a couple things I'm seeing are that yes it looks like there was too much preload on the sear spring, the tip of the spring is sitting farther back from the pivot than ideal (although too close may cause the problem Mark described), and really the spring looks to me like either it is too long for the lock or was mounted too far back on the plate - the bend looks awful close to the edge of the plate.
I'm not knocking L&R's locks or assembly, I am sure most of these work fine but obviously your has a problem. Also looks like somebody may have wallowed out the slot in the plate for the tit on back of the spring, maybe in an effort to raise the spring and let some tension off - ? The sear bar looks less arched to me in this shot, and again maybe this is just the shape of the part to begin with, but perhaps somebody heated and bent it. Did you buy this lock new?
If you're positive that the spring isn't dragging the plate (with the spring mounted, a thin piece of paper should slip behind the lower limb, and bending the shouldn't force it over to contact the plate) then modifying or replacing the spring seem the logical next step. If it was mine and I was sure the spring was the culprit, I'd close the bend slightly and re- harden and temper it. If a replacement is no different than this one, modifying may be the only option .
The reason I asked if you had tripped the lock with the mainspring installed, or if the mainspring was out and you were just pushing on the back of the hammer - sometimes when it takes excessive force to raise the sear it's because the relationship between the sear nose and full cock notch is out of whack. Without getting too involved here, a situation can exist where in order for the sear to drop out of the full cock notch, the tumbler has to rotate back slightly first which means you're fighting mainspring tension to release the sear. Makes for a very stiff trigger pull no matter how well you do everything else. A quick check for this is to take the mainspring out, pinch the lock plate nose in the vise with the tail straight up, cock the lock and very slowly trip the sear. If the hammer raises upward even a little bit before it drops, you have a notch / sear nose geometry issue.