Agent 777 controlled lamp problem

Hi,
I'm fixing an Agent 777 for somebody, my first Gameplan. It's was totally dead (missing parts, hacked..) Now it's booting and I can play a game.

I have two problems left:

- Right sling et bumper not working on diagnostic test
- Controlled lamp not working (some stay always on or always off)

I'm concentrate on Lamp right now. I think the problem is on the MPU. No lamps in diagnostic mode.
If I understand right LDU 4514 need to have low signal to be enable, but I seem to always have high so 4514s outputs stay low.

Lamp enable is coming from a 74154. On the 74154 inputs coming from the PIA I have data on pin 20,21, 23 and 0V on pin 22. So I guess the PIA or this 74154 have problems.

Since I don't want to change chip for the fun of it, does somebody have an advice how to troubleshoot this problem. Just want to understand what's happening in the section for the controlled lamps.

Thanks