I don’t think this would be classified as an issue.
If anything the ‘old way’ you describe would be the issue as changing the recipe would change consumption for past sales ie on the bases the recipe was correct but has now changed.
I have not used inventory but know there have been big changes in the recipe/inventory side of things and if this is the case that is most likely to be the reason. The improvements made as far as I understand make making recipes and getting the consumption correct should be allot easier and more flexible than the old system.
There are some comments on the inventory changes on the release notes;