Added 1uF cap to the base of the transistor that grounds the trigger on the bistable vibrator. When cranking the sensitivity of the IR proximity sensor for the drop detection, I noticed it came on when the circuit powered up or when the PIR activated when it was disabled. Ading the cap prevented this and let me turn up the sensitivity more so that it sees black plastic now :)
Also replaced the 100R to the base of the motor with a 1K trimpot so I can dial in the best motor speed for dispensing. It's still not as fast or consistent as I'd like.