Steg k2.04 blink led power and protection

Hi guys.

I am working with a steg k2.04 that blink the power and protection led.
removing the diode shown in the image, the amplifier turns on and works perfectly, so the problem must be in the protection circuit, but I have checked everything and I do not find any component out of value ... Has something like this happened?
 

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If I connect the radio to the same power supply as the amplifier and connect rca, it turns on perfectly. the voltage between the primary gnd and the rca gnd is 0v. there are no clicks or unusual noises in either of the 2 channels. It is also not seen that any component overheats.
 
Do you see a bit more voltage on one RCA than the other?

The ground fault circuit is engaging. Alpine has a similar circuit that intentionally applies voltage to the secondary to detect open RCA shields. I don't think that's the purpose of this amp's circuit. If we could determine if one channel is the culprit, that would narrow things down.

If the transistor Q40 is readily available (it will likely be damaged when removed), you could remove it to see if it being leaky is the problem.