Mk133 always resets

I assembled and connected two MK133’s and everything was working perfectly until I started to put it all into a project box. Now all the buttons activate their respective lights but they do not hold on. They go out as soon as you let go of the button. Any thoughts on what could have caused this. I was being gentle and see no signs of anything loose or broken. Don’t understand what could have changed.

If it worked before, the cause is most likely a mechanical problem (broken or loose track/pad, bad/loose soldering, etc…).
Are you sure you did not change anything after you have put the unit in a box (different wiring, power supply, etc…).

I literally didn’t change anything. I have looked and don’t see any obviously loose or bad connections. What part of the circuit is supposed to keep the lamp lit until reset? This would help me know where to start looking more closely. As I said each light lights with the appropriate button push but only as long as the button is held down. Once the button is released the light goes out immediately.

Basically, the circuit consists of 4 identical parts, one for each player.
The NPN transistor must remain active when the particular player button has been pressed, so that the level measured between gnd and the R3/R8 connection remains low (<1V).