When you create a blueprint with miniloaders in it the number of miniloaders is double the actual amount if the blueprint is currently in a blueprint book.
Way to reproduce:
Place down 1 miniloader
Take a blank blueprint and blueprint the miniloader (you will have a blueprint with just that miniloader and the count of 1 miniloader)
Now take a blueprint book and place the blueprint into it.
Select new content for the blueprint and select the miniloader again (you will have a blueprint with a single miniloader and the count of 2 miniloaders)

I assume that there is a script in the background that is checking if a blueprint is made and replacing the 2 'hidden' inserters with a single miniloader but this script isnt running properly if the blueprint is made/recreated from within a blueprint book.

At the moment I just have to take the blueprint out of its blueprint book if I want to update it before putting it back.

Yeah it's actually a bug in the engine that is probably not going to get fixed, https://forums.factorio.com/viewtopic.php?f=48&t=88100

The mod currently has a work around for blueprints directly in the inventory, but there isn't a way to fix it from the mod side for all cases. In particular whenever the blueprint is in the blueprint library either directly or through a containing book, there isn't any way for the mod to get to the blueprint. There is a broader work around than currently implemented that works with blueprints in books that are in the player inventory but it's even more of a hack than the current implementation. I have been using it locally but hadn't submitted it as a PR because a) it's really hacky and b) I wasn't satisfied that it won't cause other problems.