Question Gigabyte X570 Aorus Master + 5700 XT POST issues

[nooneisback]

I have an Aorus Master X570 motherboard and a Sapphire RX 5700 XT Pulse GPU. The issue happens about 1/3 times when turning on. The PC won't POST and requires a few resets before being able to POST again.

I first suspected a faulty PSU, but quickly dismissed that by having the same issue appear with a different one. I then suspected that the GPU, but that was also proven wrong since my older build could boot properly 20 times with the 5700 XT. I finally tried booting with my old R9 280X and didn't have a single issue. It seems like this motherboard just doesn't want to run normally with my GPU.

Since this issue is fairly old (since last summer), I tried multiple firmware versions and it helped a bit (didn't want to POST at all at the beginning), but the issue still persists.

Specs:
CPU - Ryzen 9 3900X
Mobo - Aorus Master X570 - firmware ver. F31q
RAM - Kingston 64GB
GPU - Sapphire RX 5700 XT Pulse
PSU - Corsair RM 1000X

 

[nooneisback]

Update:
I managed to fix the POST issue by setting the PCIe mode to gen 3; however, there are some less important issues that persist.
If I try setting my PC into sleep mode, it just reboots (no BSOD) and the GPU motherboard light is on. Whenever I try setting it to hibernate, the GPU light is on again, but it just gets stuck until I cut the power. There are no crashes, and all benchmarks run successfully overnight.