Finding a gunsmith who will/can work on those guns is hard. The few who can are thin on the ground and have stacked up work. (As you found out, some gunsmiths will not admit they can't fix something, so they try. And screw things up worse.)
I don't think Colt will even work on those old guns any more, but you can try calling them and maybe they have service locations. Another possibility is Cylinder and Slide, but they also are backed up.
Just FWIW, it was pretty common for brand new Colts to not fully lock up IF cocked slowly and the cylinder was retarded. They would lock up fine when the trigger was pulled through the final fraction of an inch and the firing pin strike would be centered. There has been a lot of bad advice "on the net" about those guns, to the effect that they should always lock up even if the cylinder is held back, and that any gun that fails that test is bad and must be worked on. Many times, the person who does the work makes things worse.
So, if the gun functioned and drew up when used normally (no pipe wrench on the cylinder) and the firing pin strikes were centered in the primer, the gun is/was OK.
Jim