We’ve further stumbled upon some issues, and while I can’t fully articulate them, I can hopefully give some pointers.
Somehow, we’ve ended up with a different recordID for the schema_migration models on staging and uat.
This is probably what’s causing the migration:new script to want to re-create the schema_migration model, even when it already exists.
I think we mixed updating our records by clicking in the web interface with creating them with migrations, and this is the root of what’s causing us major issues in using the migration tooling.