Hi Dj Turko, I had the same problem as you. The headphone output was extremely loud and distorted, even though the tracks were playing between 0 and 9 dB (so the vu meter never touched the red LEDs). The problem, as far as I remember, was exclusively on the headphone outputs. I tried the XLR master output with my Genelec 8030s and they sounded fine. I tried various types of headphones and, of course, both jack outputs.
I returned the item to the seller who actually recognized the problem and sent it in turn to an official Pioneer technical support center. This was because the seller didn't have any others available in stock, as this model still hard to find here in Europe).
It seems that Pioneer, as has been communicated here on the forum by a user, is also suffering from the global chip shortage and is having trouble meeting launch and delivery times for some products.
Right now my RX3 has been at the technical support center since January 10 and I have no further news about it. At this point I'm hoping it gets back to me as soon as possible. Really unexpected from a company like Pioneer on a product of this level... especially after the money I spent I was hoping to find a flawless product as many of their other products (although I am aware that technical problems can happen to everyone).
I hope to have been helpful!