Samson servo 500, clip light on

[Vicus]

I'm struggling with an amplifier model servo 500 by Samson. It came in with clip of one channel on and the protection led on. The "protection" problem was due to a burned resistor (too low in power rating) but the clip light is on due to an dc voltage on the output. The schematic can be found here: https://elektrotanya.com/samson_audio_servo_550_130w_stereo_pa_sch.pdf/download.html witch is at 95% identical.
Now I think that is normal that the input differential keep (with the integrator, look at the opamp) the output dc offset near zero. What I don't think it's normal is that the clip light stay on. The theory is that if the difference from the output signal and the input signal is to high (aka distortion) the clip light came on.
Correct me if I'm wrong, the input stage is a symmetrical differential driven by a current sink eatch one. So if one of the two transistor pair conduct more current the other lower so that the sum of the stage is costant. Right? Now i did measure that the upper stage a have 2.0 and 1.3 V on the 1k resistor but in the lower pair i have valure very close like 1.43 and 1.45 (voltage vary with temperature). I check every resistor and they read fine. I disconnect the integrator and sam thing but with more dc offset at the output. Output bias is ok, every stage is in linear region. In my case the upper NPN pair is discete and the lower PNP pair is the same package.
Some idea?
Thanks, a lot.