If an item doesn't have a definitions section, the LCs create one that has an extraMaterialLists with only one entry, which then mismatches if you have more than one entry in materialLists.

I would suggest doing the selection of a valid list first, then combining the base list with the extra list to reduce mismatching if possible.

Eh, the correct thing to do is to make LCs smart enough to notice the multiple materialLists and correct for that in the auto-generation of the extraMaterialLists

Addressed in 22.9.0.