Pioneer vsx-420 switching of when I turn the volume over 50

Hi, I have a VSX-420... the unit switches on... Even with one speaker connected to the front or center... As soon as I increase the volume it plays up to about 48,but then Amp switches of when I go beyond that. I did try the factory reset... Please help

Good Day,

Thank You so much for the pointed answers to my request. I ended up taking it apart to get some decent photo's. I must say I could not find any swollen components or something out of the ordinary.

I removed the backplate to expose the big caps etc for pics, and then out everything back together.

So here the thing😉.... I had called my niece the previous night and told him I have a few items thats going to the bin, he came the next morning while I still had this unit open.. I put it back together and he took it with him.

• Guess what video he sent me later in the day😳... Without doing anything... The Amp now just works... He cranked it up to 70...and it's still pushing.

Pity I can't upload the video clip.

Anyway, Thank You again... Guess he was meant to get a present from his Uncle😊😊