What's with the weird RAM problem?

Question

Iron

So, there is a motherboard in which there are two slots for RAM. There are two bars - 1 and 2.
Further I will use the following designations S1 and S2 - Slots one and 2, respectively, R1 and R2 - RAM bars 1 and 2, respectively. The sign -> means that such and such a plate is inserted into such and such a slot.
Further experiments:
Experiment #1
R1 -> S1
R2 -> S2
Outcome: everything works in 70% of cases
Experiment #2
R1 -> S2
R2 -> S1
Outcome: does not work in 60% of cases
Experiment #3
R1 -> S1
R2 - > not connected
Result: everything works
Experiment #4
R1 -> not connected
R2 -> S1
Outcome: not working
In those cases when it works, that is, it is possible to start the PC, the Windows memory test shows that everything is fine with the memory. It is not clear, it seems like the second plate does not work, but when it is possible to start it, the tests show that everything is fine with the memory.

Answer 1

the connector is loose, the pads are oxidized - non-contact.
the bar is bent / overheated - one of the contacts of the microcircuit has fallen off the board - the result is the same.
the memory chip itself is defective - a defect in the plate, the DRAM capacity quickly loses charge.
on the motherboard, the memory driver is buggy
and a bunch of other floating errors.
set the memory bar for a couple of laps with a minimum to drive memtest + without Windows and other operating systems.

Answer 2

Damn, well, it's obvious that the R2 bar is not working!
run memtest