Memtest did not detect any errors, although the memory is not working properly

[RamRabbit]

I am using the free version of the program, memtest did not detect any errors. However, the Silicon Power memory is not working properly, or they cannot work together. Windows 10 crashed into a blue screen every time. After I removed Silicon power and left one Crucial, the system became stable. I guess they just aren't compatible together! But why didn't memtest see it?

DDR3 RAM

SP004GBLTU133V02 4GB
CRUCIAL CT25664BA160B 2GB

[David (PassMark)]

Could be some electrical or environmental trigger. e.g. EMI or temperature related, and whole system runs hotter in Windows than in MemTest86.

I assume full 6GB was being tested in MemTest86 and 6GB was also available in Windows?