I've been learning about the delayed-choice-quantum-eraser experiment. To sum up; I imagine a double slit which has behind it a crystal which splits photons into entangled pairs. The crystal sends a photon to the right, from either slit, toward a single sensor (s1) which simply measures that a photon was received and in a pattern, and then the crystal also sends an entangled photon to the left, presumably from the same slit to an apparatus that allows the entangled photon to be detected (s2, s3) based on which slit it passed through 50% of the time, or the entangled photon is reflected into a path which combines both slits into a single censor (or set of sensors, s4 and s5 which cannot determine which slit the photon passed through).
I was watching a laymens video which made the claim that the crystal, in a sense, is making a measurement when the photon passes through it and the entangled pair are created, therefore an interference pattern cannot be made at sensor 1. This was new to me, hearing this interpretation. Part of my confusion is that I am under the impression that sensors 4 and 5 are showing interference, and this seems to contradict the claim that the crystal is collapsing the wave form. My question is; what if sensors 2 and 3 are turned off, or completely removed from the experiment/apparatus? Does sensor 1 still have no interference? I'm assuming sensor 4 and 5 still have interference.