It's the measurement problem, I think? Energy is moving as a wave, but the energy can only be transferred in quantum-sized values. At some point it "collapses" to a particular interaction with some other wave, and we can only probabilistically calculate where this may occur.

Edit: the Bell experiment is something else. It's like a wave can exist as an entity outside of time and space and only comes back to reality when it interacts. Perhaps it would make sense for electromagnetic waves if the distance and local time elapsed contracts to zero per relativity when travelling at the speed of light.

The measurement problem is a different kind of weirdness, that may or may not reduce to the same explanation after we have it.

The problem with the double slit (and Bell inequality) is that real things that we can see are correlated, not about mixed states and state erasure.