Hi RiverFire,
I appreciate the additional details you’ve provided. Custom Lists and Custom Fields should export consistently for any item where those fields are populated, so what you’re seeing with only some items missing that data is definitely not expected. I'd recommend reaching out to our back-end team so they can take a closer look with this. You can reach our Live Chat team via our virtual assistant, MOCA or by submitting a support case via MyAccount.
You can also visit this help article for more information about: Exporting items
Regards,
Earl