Aliasing foldover problem

Hi everybody.
Firstly, some words about my project.
I'm working on some insane idea - reversed subtractive/additive synthesizer based on noise as source.

And additive possibilities is my main problem for now.
I can't figure it out why my poly~ object is distorting signal on high octaves (see screenshots with spectrum), even if i'm upsampling it to 8. I think that it is happening because of foldover, but i'm not sure about that. That is why i'm asking for you to help me.

Also i really can't understand the nature of clicks that are appearing when i'm triggering the notes with low attack values.

I will be very thankful for any advice or any direction to what info should i dig, about this problems.

On screenshots, as you can see there is a huge amount of low frequencies when i'm triggering high notes. Also sometimes this gaps covering all spectrum. And sometimes notes playing to louder then it should.