The trapdoor is a tricky piece of technology to get right. It took me about 5 goes to get it right, but I can advise you can fix it. I had multiple issues with mine.
1. I could get the mechanism to "pop" and "drop" perfectly while testing but it would keep reporting as failed during game. Turned out that the switch wire underneath wasn't quite bent right, so the state of the trapdoor couldn't be read by the switch.
2. I also had a lubrication issue which made the door mechanism very stiff, but some silicon grease which I use on my TZ clock fixed that.
3. The third thing that went wrong was the centering of the solenoid on the release mechanism wasn't sharp. The baseplate was crooked with respect to the plate, meaning the latch didn't hold onto the blue arm when extended and therefore didn't release properly. This was just a simple phillps head screw loosen and tighten
4. The final problem was that the latch plate on the door release solenoid was loose. There are two mini phillips screws on the release plate that hold it to the plate. If yours was loose like mine was, it causes the door release flap to slop around, meaning it doesn't release properly. You can feel it being wonky if you have this problem. You have to take off the release solenoid to access the screws.
I've fixed all of the above and it now works and has worked for well over 100 games without a hiccup. Hopefully this can help you or someone else.