if you dd on another usb-drive the same data -- will it stay the same? if yes -- you could post it somewhere and try to get more details etc.

I've seen a feature phone do this as well, when "powered off" in charging-only mode.

Oh hey, I had one of those too. I eventually smashed it and threw it out because I tired of plugging it in and having slow down problems.

(I noticed it first when I was working with the jump drive and had the system grind to a halt. Removed the drive and it immediately unfroze. further testing confirmed)