Give me a little while to check it out on my RPi, and see if it needs a recompile. Which OS is your RPi using?
Could you try the new upload I added, “premium_nano4x_v1-0-0_64_raspi.zip”? If this works I’d appreciate knowing as I might need to go back and recompile a lot of my older games.
I checked through some of the build notes and it wasn’t until later versions that Pico8 supported 64bit, which the original builds were done beforehand. I’m hoping this fixes your specific problem.
Oh, and a lot of the core code is available for to view over at https://www.lexaloffle.com/bbs/?tid=43838, that’s effectively the browser version which excludes the paid for content.