How to Copy Multi to another multi

Multis 1-16 are special and cannot be stored to other locations, could this be the reason?

Unlike regular multis that simply reference existing patches (in RAM or ROM banks), multis 1-16 actually contain the individual patch settings within them. As far as I know, the only solution is to first save all patches you're using to RAM, and then recreate your multi as a regular one referencing those patches. I'm not aware of a way to edit multis on a computer.