ASRock Z790 PG Riptide PCIE Gen 5 x16 does not wor

Motherboard: ASRock Z790 PG Riptide (I bought two of these, both have the same problem);
GPU: RTX 4070/4070 Ti;
PSU: two different 750W Bronze and Gold;
CPU: 13600KF;
RAM: G.Skill 5200 MHz 16x2 CL36/6400 16x2 CL32;
SSD: I tried two new KC3000, thinking that the problem was in them.

I am assembling two computers for 4070 and 4070 Ti with 13600KF and the same motherboards - Z790 PG Riptide.

After much manipulation, I realized that the problem is with the matplate in the Gen5 x16 lines slot - the video card is not detected correctly in it. Windows gives an error that it cannot detect the graphics adapter and restarts pc. Or just black screens and reboots altogether.

As a result, I installed the video card in the Gen 4 x4 line slot (slot x16) - the video card works, but in 4-line mode. And then, when you turn on the computer, there are moments when the picture disappears, as the system loses connection with the graphics adapter, but as a result it works and there are no reboots.
But using a pcie x4 line mode graphics card in the lower slot literally lying on the case does not suit me??

What should I do? Two identical boards and the same problem. I saw a similar topic here where other people wrote about this problem on this board back in 2022. Is it still not fixed?

On one motherboard, I updated the BIOS to the latest version, but it didn't help.