Do a quick test.

Repeat the slide drop, and follow these steps.

Slide in-battery...Thumb-cock the hammer and dry-fire the gun. Don't release the trigger. Hold it back. Rack the slide and release, like a slingshot
reload. If it doesn't follow, lock the slide to the rear...pull the trigger and hold it. Release the slide with the slidestop. If it doesn't follow, the trigger is nudging the disconnect and rolling the sear out of the hammer hooks, and probably a little sear bounce is contributing to it. Increase forward tension
on the center leaf of the spring and retest without holding the trigger back.
If it follows, increase tension on the far left sear spring leg to get a little more tension on the sear...and retest without holding the trigger. If it still bounces, install a new 23# mainspring.

If it follows with the trigger pulled and held, there's a problem with one or more of the main three parts in the fire control group. Hammer...Trigger...or Disconnect.