Welcome to the ROG forum.
It's not recommended to combine memory kits and this is what is likely giving you trouble.
Remove one memory kit and give it a try, or if you must have 64GB, lower the Dram Frequency.
So, you've already tried lowering the frequency with no success.
32GB is more than enough for games. Try with one kit in slots A2 - B2, you'll have a much better chance at achieving stability at 3600MHz.
Question is even if all ram kits are the same one?
The QVL has some recommendations for 4 DIMM configurations, if you need to go that way. Filter by "Socket Support" 4 (and remember to select Ryzen 5000 series). I'm happily running 4x Crucial Ballistix BL16G36C16U4B 16GB DDR4-3600 CL16 on the Crosshair VIII Extreme (which is also X570S, like your Dark Hero, essentially the sibling board). 4-way is a bigger challenge than 2-way, so some kits that are good for 2-way just won't easily do 4-way even if they are all identical down to the same batch. Those Crucial DIMMs are Micron DDR4-2666 CL19/20 in their basic JEDEC SPD configuration. Crucial don't sell a 4-way kit, so I had to risk buying 2x 2-way kits, but ended up with 4 DIMMs with the same hardware revision and very close serial numbers; I would have bought 4-way if I could have found it, but those were the best 3600 CL16 on the QVL that I could find in stock at the time.
Unfortunately, your G.SKILL DIMMs are not on the QVL for 4-way. That doesn't mean they won't work, especially if you are willing to lower the clock or loosen the timings, just it might be more of a challenge.
Edit: one other thing to try is the way the 2 kits are mixed. With kits X and Y, XXYY vs XYXY might get different results. The DIMM serial numbers should hopefully let you identify the 2 different kits, if you're not certain which are which. Try a reasonably long MemTest86+ with each config.
My rams is currently XXYY didnt try XYXY or just A2-B2 take one set out but i will try also memtest86, what should i expect with the memtest86 ?
All right sounds good,
I'm looking forward to your results.