LD Zone 622 2-Zone Rack Mixer Repair The customer says it is faulty but does that mean he is right?

A Customer brought this 2 Zone audio mixer for repair, It has some problems but the fault I found on it is not the same one that the customer wants me to repair. Is the customer always right?

I used this free audio sweep generator online https://onlinetonegenerator.com/frequency-sweep-generator.html it works OK but whoever programmed it forgot to put a repeat button on the sweep function!

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Видео LD Zone 622 2-Zone Rack Mixer Repair The customer says it is faulty but does that mean he is right? канала Learn Electronics Repair