I own a PTR 9CT and SB Tactical SBT5A pistol stabilizing brace.. Even with your description, I'm unable to figure out how you managed to get that malfunction. It sounds like you forgot to attach the buffer spring and guide rod behind the bolt carrier assembly. NOT in front! The spring/rod combo keeps the bolt carrier assembly firmly pushed forward, and it takes some effort to lock the cocking handle to the rear.
If you are reassembling it correctly:
- The bolt head (silver) goes into the receiver first, guided by the black bolt carrier which rides the grooves of the receiver. The buffer spring/guide rod are seated behind the bolt carrier and will stick out a little bit from the back of the receiver
- Attach the lower housing next, because the bolt carrier assembly won't slide down if the housing came first.
- The end cap of the SBT5A brace will attach to the rear of the receiver/pistol grip. The buffer spring will touch the dimple inside the end cap.
If you pull back on the cocking handle, you should feel a firm resistance and the buffer spring would return the bolt carrier assembly back into place when you let go.