MOD GC - Tried everything! no success...

Hi All,

I'm having issues with my GameCube(s).
I'm having read errors constantly or discs are not seen/started.

I tried for as far as I know now everything that can solve this:

# I used diffent MOD chips - Viper Extreme & the Qoob SX
# I used different BIOS versions
# I tried it on 3! different GameCube`s (version A/B & C)
# I even bought a new GC lens
# I used different media (also the Ritek G04 discs) and different burners
# I did the lasertweak on all 3 GC`s.

Is there any other thing I can try? I had a black GC in the past that was reading just everything.
I tried a lot as you can see, and am getting frustrated cause of buying 3 different GC's/chips/lenses/disc etc.
Can someone help me?

Thanks! :)