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It was likely the XDJ that had the issue, but hard to say what caused it.
Yes, you can use SSDs as they're pretty much the same as a USB drive, just with faster / larger memory modules and a different memory controller. I personally love the Samsung T5 / T7 drives, but there are lots out there which are very reliable and offer a great bang for the buck.
Black Friday / Cyber Monday is a fantastic time to upgrade your storage!