Thank you guys for all the info, this helped me a lot as well. Although I still have some circular dependencies, it seems unreal was unhappy about a few very particular ones. The plugin mentioned above unfortunately just caused the engine to crash for me, but the reference viewer was super helpful (just look at a copy of the same asset on both sides).
While the plugin didn’t work, the info provided on how to fix circular dependencies was super helpful: GitHub - bstt/CircularDependenciesDetector: Documentation and source code of Circular Dependencies Detector UE4 plugin.
All in all, I hope unreal did a better job of warning us about this situation. Especially since it stops you from packaging all together.