Super Lead clone - lack distortion inside head box

[Omn]

I built a Super Lead clone (Metro Amp) way back. And it has this strange "application"; as soon as it gets inside the head box some amount of distortion disappear. Tried "chop stick"-poking all the wires and components. No cracklings. Tubes seems fine.
What I am left with is the metal plate at the inside bottom of the head box. Good for cancelling interference. Noise reduction and maybe better grounding (not all convinced about that - but it is a guess). Could this plate also reduce distortion? And if so; why?

It is just that my amp seems to like the open air...

Any help is appreciated

[Omn]

Found the solution on another forum.
There are two wires coming from the output transformer that are not in use. I have curled them together, held by strips and heat shrinked the ends. I find no scars in the wires or the heatshrinks. Can not see any wire...
Well. This "bundle" of wires have "traveled" and got in touch with the metal plate, and somehow grounded.
Solution was to cut them both short (1 cm) and heat shrink the ends.
Amp is as good as in the cradle.

[Wilder Amplification]

There shouldn't be any wires that aren't being used on the output transformer. Were you referring to the two unused primary wires on the POWER transformer?

[Omn]

Oh boy... Yeah Jon; power transformer (1203-80-ML).

Thank you!

[Chuck H]

There shouldn't be any wires that aren't being used on the output transformer. Were you referring to the two unused primary wires on the POWER transformer?

That would depend on the transformer. I often build with off the shelf Hammonds that have UL taps which I most often cut short and shrink tube. But I made this assumption reading the OP and was wrong as it turns out...

Chuck