MemTest86: there are errors with 4 sticks, but no one at a time?

Question

Iron

System:
Asus B450 Pro Gaming
AMD R5 2600
4x 8Gb Kingston Predator DDR4 (LED) (3000Mzh)

Browser crashes (opera) and frequent bugs.
It all came down to RAM.
It was possible to start a computer with this processor and four bars only at 2666 MHz. (By the way, I tested it on R5 3600 - it started up and worked even at 3200 MHz).
Passed MemTest86 (without +) - errors on the sixth test (block movement, 64 bytes).

I decided to single out a specific bar, started to drive one at a time (at a frequency of 3000) - the bars passed the tests.
I scratched my turnips, blew out the connector, inserted all 4 again, ran the test. 4 runs - no errors.
Was already happy. Maybe the contact where it was bad.
The evening of another day, I start the computer, turn on the browser, the opera errors again, I run the memtest - again errors.
Where to dig?

All straps are under warranty, but should all 4 be carried to the SC?
Proc without overclocking, everything by default, except for RAM (starts at 2400 after reset, I set the wired profile to 2666).

Answer 1

It was possible to start a computer with this processor and four bars only at 2666 MHz.

Who promised you more?
The motherboard spec says:

4 x DIMMs, max. 64GB, DDR4 3533(OC)/3466(OC)/3200(OC)/3000(OC)/2800(
OC)/2666/ 2400/2133 MHz, un-buffered memory

OC = overclock, overclocking.

Answer 2

Unfortunately, gen 2 ryzen are quite finicky when it comes to RAM.
As you yourself noticed, everything works fine with the third generation of Ryzen. In the third generation with RAM support, it is much better (I changed r7 2700 to r7 3700). Most likely, your kit will work stably at 2400 (what is indicated in the SPD), but, in my opinion, this is not the best option for your processor.
You can try:
1. Replace the RAM. The whole set. Choose exclusively from QVL.
2. Replace the processor - with something of the third or fifth generation.
3. Experiment with overclocking RAM (and in your case, this is just overclocking). Perhaps the
DRAM Calculator for Ryzen will help.

Answer 3

If you bought 4 identical dice as a set, then in theory they should have the same timings, but since you say that the timings are different, it’s probably loose from different batches ...
In a cpu-z program, look at what timings for the dice are registered in spd, remember parameters of the worst chip (the highest timings) and set these parameters forcibly in the BIOS for all 4 memory sticks.
In theory, this should solve the problem when SPD is read from a fast die and set to a slow one.
If it helps, you can try higher frequencies, the principle is similar, you find the operating frequency and parameters for each plate and set the slowest ones for everyone.
PS
Check the voltage according to the passport (they googled the dies on the long part number) and compare what is in the BIOS, it may be set incorrectly in the BIOS, too low / high voltage can interfere with work.