After updating the game and IR2 / K2 to the latest versions, I get quite a few load errors when loading this mod in combination with Industrial Revolution 2, Industrial Revolution 2: Stacking Beltboxes (support for this mod) and Krastorio 2.

Only disabling this and the IR2 support mod will let the game start.

You will need to report those errors (in considerably more detail) to the K2 maintainer. Stacking Beltboxes doesn't contain any specific support for specific mods, it provides an API for people to make their own support. The compatibility patch that lets IR2 work with K2 at all is part of K2.