B450M Pro4 not running in Dual Channel Mode

Hello,

Recently, I built a new PC for 3D architectural modeling, but met an issue. It doesn't work in dual-channel memory mode. Before I proceed, there is the PC configuration:

CPU: AMD Ryzen 7 1700
Mobo: AsRock B450M Pro4
RAM: G.Skill F4-3200C16D-16GTZB (which is in QVL support list)
GC: Gainward RTX 2060 Phoenix GS
OS: Windows 10 Home for SL

So, the memory kit is fine, I have tested it with another (but Intel i7) build and it worked well. As I mentioned above, the memory kit is in the QVL memory support list, so it shouldn't be an issue.

I tested different B450M memory slots and got the following results:
1) Memory in 2 and 4 slots runs only in Single-Channel Mode (SCM) and ONLY with 2133 Mhz. Neither XPM, nor manual settings can start more than 2133 Mhz. Memory size in BIOS and system is 16 GB.
2) Memory in 1 and 3 slots runs as well as in 2 and 4 slots (SCM, 2133 Mhz and 16GB)
3) Memory in 1 and 2 slots runs in SCM, but it can get more than 2133 Mhz memory speed, up to 2933 Mhz with 16Gb.
4) Finally, I tried to put a single memory stick in mobo each slot. The result is: system runs with memory in 1 or 2 slot, but doesn't run in 3 or 4 slot (just get black screen for about 10-15 seconds and system reboots)

I've updated the BIOS version to its last (at that time it was 2.00) but have no positive results. So, question is: is it just a defective component (the mobo) or I'm missing something?

Thank you in advance!

I am facing the same issue with same motherboard, did you found any solution?