To verify that the ram stick is faulty,
Test each individual stick in the slot that your motherboard prefers for a single stick.
Your ram will have a lifetime warranty from g.skil.
Run memtest86 or memtest86+
They boot from a usb stick and do not use windows.
You can download them here:
MemTest86 is the original self booting memory testing software for x86 and ARM computers. Supporting both BIOS and UEFI, with options to boot from USB.
Memtest86+ is an advanced, free, open-source, stand-alone memory tester for 32- and 64-bit computers (UEFI & BIOS supported)
If you can run a full pass with NO errors, your ram should be ok.
Running several more passes will sometimes uncover an issue, but it takes more time.
Probably not worth it unless you really suspect a ram issue.
But, there may be an issue since all your ram is not matched in a 4 stick kit.
It would seem that you have a pair of 2 stick kits.
Ram is sold in kits for a reason.
A motherboard must manage all the ram using the same specs of voltage, cas and speed.
The internal workings are designed for the capacity of the kit.
Ram from the same vendor and part number can be made up of differing manufacturing components over time.
Some motherboards, can be very sensitive to this.
This is more difficult when more sticks are involved.
Ram must be matched for proper operation.
You can sometimes compensate for errors by increasing the ram voltage in the motherboard bios if you have an overclocking motherboard.