I did not check the Bolt Catch spring hole with a drill bit when I assembled my DPMS lower. There must be a tiny burr on the edge of the hole. Now the bolt catch plunger (on top of the bolt catch spring) won't pop completely out under spring pressure. It will move a bit in-and-out, but it hangs up when released with only its rounded top sticking out, so it can't be grabbed with pliers and pulled out. This situation, of course, leaves the Bolt Catch just flopping around, with no spring pressure.

I am stumped. Any thoughts, short of drilling it out? Thanks in advance.

Try to deburr the edge with a drill bit or a pocket knife then drop a little CLP into the hole. Continue to "function" the detent, it will most likely come free. If not check back in.

you can take a punch and knock the roll pin out.  remove bolt catch, pry the plunger out, and remove spring.  take a burr knife and see if that helps.  if not just take a little material off the plunger.  CLP wouldnt hurt either.