F5 Turbo self-oscillation in low frequency

I'm finishing assembling my second F5 Turbo in a hybrid version, a V2 with transistor V3 driving.
the power rail increased to 39V with mosfet stabilized power supply.
During the tests I noticed a self-oscillation on my analog instrument connected to an 8ohm load when injecting a sine wave signal below 120Hz.
The blocking capacitor (C3 C4) for the self-oscillations I have tried various values from 560pF to 1.5nF the self-oscillation remains. Has anyone noticed a similar thing on their F5? Thanks to all who want to participate. Sorry in advance for my english google translate
 
Some pictures of the current construction
 

Attachments

  • 20230125_214034.jpg
    20230125_214034.jpg
    562.8 KB · Views: 95
  • 20230131_211704.jpg
    20230131_211704.jpg
    438.9 KB · Views: 93
  • 20230131_211720.jpg
    20230131_211720.jpg
    560.8 KB · Views: 93