...okay the fact this cartridge game is the only one I've had this issue with & it's not showing up in Checkpoint either made me remember it was always finicky. I think something in the connectors for it crapped out.
So went to go play some Bravely Default. Put my cartridge in, boot it up, get the screen you see. I do have Luma & the like on my New 2DS but don't know error code stuff enough to know what is actually wrong. Please help.