According to your testing, does the issue occur with ONLY MiniScaled mod and Immersive Portals mod and Farbic API?

No

Describe the issue

When playing as a Phantom in the Origins mod, being in phantom mode will make you fall through the box's floor, even if you add the 'unphaseable' tag to mini_scaled:barrier with a datapack.
Placing a layer of normal blocks inside the box prevents this.

Post the log here

No log, because no crash.