May I ask why you say 'probably'? Also, I don't know how your BIOS is set up. But you are in UEFI Mode. Try creating the memtest86+ USB drive by downloading the pre compiled USB version of Memtest86+. I will give my typical instructions below. If you use the one time boot menu Key, if you have 2 options for your USB drive one will say just the make of your USB drive and the other will say UEFI and the name of your USB. Choose the UEFI Entry.
If that does not work, in your BIOS, disable fast Boot and set your Secure Boot setting to Other OS or which setting you have that will recognize both UEFI settings and MBR settings. Set the USB drive as first boot device (it has to be inserted before booting into bios to be recognized). After the test, you can change everything back to like it is right now.
I realize, this sounds complicated, but it really isn't. These are my typical instructions.
Please Run Memtest86+
Please download from this site only http://www.memtest.org/
in the middle of the page are the Download links, you can download the ISO.zip or the Auto USB Flash Drive installer.zip
Extract the Zip file. If you chose the ISO image, burn it to a CD using Windows Disk Image Burner or any Image burner you may have. If you downloaded the Auto USB installer, extract it, insert your USB 2.0 Flash Drive and take note of the drive letter. Run the installer, select the Flash Drive Letter, check the format box and press next. It will install memtest86+ to a flash drive. You can use either V4.20 or V5.01. Boot from your selected media. If you use V5.01 it will tell you to press certain buttons at the start, please press no buttons. The test will begin on it's own and continue to run until you stop it. It needs to run for 8 complete passes or until you receive an error. If you receive an error, stop the test. Even 1 error is a fail. Each pass tests a different part of the ram and each of the 10 tests in each pass tests something different. It takes a minimum of 8 passes to completely test the ram, more passes are better. It is quite a long test and will take several hours depending on how much ram you have. Due to the time length it is best to run overnight. If you have any questions, please do not hesitate to ask