Export main -> exports a save file as it was loaded in PKHeX.
Export backup -> exports a save file with the .bak extension, only useful for backups
I also cannot replicate this issue; restoring this save file works fine on my end. As mentioned by @theSLAYER, you can try deleting the secure value and trying again. In JKSM, do the following:
Cartridge (or SD/CIA -> Pokemon Moon, depending on your game) -> Save Data Options -> Delete Secure Value
After doing this, please report back and see if this has fixed your issue.