Big trouble with Pre Phono 2

[LSfarzo]

Hello...
it's a lot of time I do not write on the forum. Hope you all are doing fine!

I'm in big trouble with my (old) WAD Pre Phono 2. The Pre has 2 sowter 9570 step-up, PIO and jensen caps, as can be seen in the photo.

It souded really great (but really !) coupled with a Benz Ace L.
I also matched the load for this cartridge.

Some time ago the sound chnaged suddenly. It is like there is a sort of "cut" to some mid and low frequencies. It has suddenly turned harsh and bad, like if the cartridge is not able to track the LPs. The sound is definitely "packed" and unpleasant... it is bad, like something is not working anymore.

I sent the cartiridge for a complete check and it was cleaned and tested by a very well kown and good cartridge master (i do not write the name to avoid unwanted advertisitng...).

The cartridge has come back and the things are getting only very slightly better.

I think that the problem is with the phono preamp.
The WAD Pre works fine.

Now the point is: do someone has some smart idea about what I could do? I do not want to start changing things .. I could end up losing a lot of time and money !

The strangest thing is that this behavior affect both channels !

Every idea is very very well welcomed !

Regards
Luca
Italy