It could be an underspec or mismatched DDR3L stick.
I would try cleaning the DDR3L connectors with an electrical contact cleaner. Stabilant-22 or DeoxIT work best. Non-perfumed isopropyl works, but it's a weak solvent so some scrubbing might be required. The old pink eraser trick can indeed scrub contacts clean, but it's widely discouraged due to ESD concerns - I'll admit that I think the risk of ESD damage is vastly overrated, but my main concern is that the rubber can also erase a few microns of gold plating off the contacts.
Clean out the RAM slots too, if you can. But if you're not confident about this then it's probably best to not tamper with what works.
I don't know what "Ignore" will do to memory training. My experience has always been that quality RAM doesn't really need training. But then again, I tend to buy overrated memory and let it run at the fastest speeds natively-supported by the chipset PCH or CPU iMCs.
You could also try replacing ye olde CR2032 motherboard battery. I know it seems irrelevant, but it can magically fix all sorts of apparently unrelated system ailments on older motherboards. 3-packs cost $1 at the local Dollar Store, lol.
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