I'm a retired watchmaker/gunsmith so I stoned the angle on the sear to a slightly different angle.
That seems to have corrected it.
When set up correctly a sear should slide back into full engagement if the trigger is released after a partial pull.
This is all about having a correct angle on the parts so the angle will force the sear to slide back into full engagement.
When wrong, you get "trigger hang" or a unsafely light trigger.
The old gag of stoning a part strictly by eye is seldom a good solution. Even for a pro, getting and keeping the surface perfect in all directions is verging on impossible. I've seen a few old timers who could do a near-perfect job on a jewelers graver by hand, and I learned how to do it in watchmakers school, but it ain't easy.
Soon as you've "learned it" you get smart and buy a jig to take the human element out of it.
One trick for stoning sears when you don't have an actual stoning jig, is to use a small vise with precision smooth top jaws.
Put the part in and position the surface above the jaw by a tiny bit, then tip the part in the vise to set the angle.
Tighten the vise, put a smooth piece of drill rod on the other end of the jaws to act as a roller, rest the stone on the area to be stoned and the roller and just slide it back and forth.
Done carefully this works well, and did this time too, certainly better then squinting at the part while using a stone by hand.
Having some serious watchmakers magnification and a good bench light helps. Can't fix what you can't see.