Rack 6 channel flickering

[Turtle]

Hello,

 

I have a strange thing on one dimmer rack 6. Channel 3 only flick at full power, but if another channel is also on, it stay stable. From 0 to 80/90% is seems working fine.

All solder look fine on the bottom. I'm not sure replacing the traic and the 12V zener diode was enought to cure the problem.

 

Connected on 3 phases main power suplly, for the test with 75 W lamp on each channel.

 

Does anyone have an idea ?

 

Thanks