Volume problems JTM45

[flyingpig]

Hi all.

I build a JTM45 from scratch ( with the Metro PDF manual )
Build the cabinet, plied the chassis, etc .

The build is niow complete but I hav a volume issue.

I did all the testing, voltages etc wher all good, bias OK.
When now playing the amp volume goes up and down, it fluctuates .

Can some help me finding this error.
Wher do I have to check the wiring , ... etc

Thanks