There were two grates - I would speak of gratings - A and B following A so that particles went through A first. B was removed and put back randomly. If both gratings were in place, the incoming He atoms chose one path through A and behaved like a particle. When only the grate A was in place, wave behaviour was observed.
What looks paradoxical is that the addition of B forced particle behavior although the incoming He atom was already gone through A and selected wave behavior. The geometric past of the particle was changed from wavelike to particle-like! As if state function reduction would change also the geometric past of particle and quantum states were superpositions of classical time evolutions rather than time=constant snapshots as in the ordinary ontology!
This is what zero energy ontology (ZEO) indeed postulates so that the findings can be seen as an additional experimental support for ZEO. In ZEO quantum states are superpositions of time evolutions and "big" (ordinary) state function reduction (BSFR) selects new superposition of classical histories with opposite arrow of time: the roles of cause and effect for classical time evolution are apparently changed. ZEO solves the basic paradox of the quantum measurement theory. Also the weird looking findings of Minev et al can be explained in terms of the time reversal occurring in BSFR(see this).
Effect precedes cause: here cone for instance explanation for the findings of Libet challenging free will: the neural activity preceding act of free will in geometric time will is caused by free will initiating a superposition of time reversed classical time evolutions in the geometric future of the brain! The geometric past is changed.
To avoid paradox, one must keep in mind that "small" state function reductions (SSFRs) give to the experienced time correlating but not identifiable with the geometric time. In the experiment, the BSFR corresponds to a removal or addition of a grating and changes what happened before the addition/removal of grate - "before" in the sense of geometric time. Removal/addition is in the sense of subjective time of the experimenter.
For a summary of earlier postings see Latest progress in TGD.