DUO1 Modchip problem

Hello,

I installed a DUO Modchip in a v4 PS2.
It played PS2 and PSX games after installation, but now
it doesn't play backup games any more, only originals.

I measured the voltage on all Duo contacts, there's 5v, GND works, and all other pins give me ~3,6 V. Only Z pin has nothing. I measured the soldering on Z pin, it is okay!

Now what can I do?

 

make sure you backups are good and all wires are going to the correct places and soldered good .

 

I have resoldered everything.

OK I tested around and found out that 3 from 10 boots work.

How does it come that only sometimes backups boot?

 

poor media , week or dirty laser .