Some very good answers above.
The 1911 trigger has several points where tolerance stacking and wear can produce trouble.
After you eliminate the disconnector as SargeMO suggests, if the trouble persists look at the sear spring. The left leaf, see if its touching dragging on the frame. A small amount of contact there can make a huge difference.
Please come back and let us know what you find.
Good point. If I'm trying to achieve target trigger, I also polish both contact surfaces between the mainspring and fire control components.
This would be a good time to add I ain't a 1911 Guru, eggspurt or custom gonne-smith. I'm just an armorer level gun mechanic who's rebuilt a pile of them for self and close friends and learned a few things along the way. Kuhnhausen's books on the 1911A1 are money well spent for folks interested in this pistol, and a much better source of info than I am.
Thats me, 35 years of fooling with 1911's. IPSC when I was younger and also poor led me to working on my own stuff. I was lucky enough to have gunsmith friends along the way to keep me from screwing up too bad.
You're right on the sear spring, You could write a short book on prepping just that one part. The middle leaf where it contacts the disconnector is sometimes so sharp it shaves metal off the little ramp. Amazing how the small things affect how well and how long the trigger components last.
A long time friend brought me a new-ish TRP that he paid a "smith" to tune the trigger. It came back worse than when he left it. The guy had cut the escape angle to almost 75% of the sear face. It would break at 3lb one pull then 1.5lb the next. He didn't catch the left side of the sear spring digging into the frame. Replaced and correctly fitted new sear and relieve the side of the sear spring and he left with a nice consistent 2.75lb trigger.
If that guy had shortened the hammer hooks any at all he would have created a full auto. Won't far from it anyway.
Good stones, jigs, tools and a magnifier are a must if you want to fool with the 1911 trigger. Especially the sear to hammer engagement.
And like you I'll add that I'm by no means anything close to an expert.