Can someone explain the anatomy of the interior of carve tight spindle?

On my latest carve, my 1/8" cutting bit broke at the conclusion of the carve. That may have no bearing on my question. but when I tried to insert another bit, there seemed to be significant resistance. I continuously loosened the tightening screw and finally removed it. When I feel inside the collet with the tip of my pinkie, there seems to be something flat inside. Is that part of the tightening mechanism? Have I dislodged something? The tightening screw doesn't seem to want to tighten completely, and I certainly don't want to strip the threads. I've tried to look at the opening with a mirror, but I can't get a good view.

I've had difficulty recently with bits sticking in the collect, and have often had to crank down on bits using the split collet adaptors in order for them to stay in place.

Any suggestions?