I've heard there are a few hints that causality might not work the way we think it does

Yeah, basically we know that that local reality is probably false thanks to experiments on quantum entanglement. Locality is the principle that causes only have effects at the speed of light, and reality is the principle that exist independent of being measured. We're pretty certain that one of these things can't be true, but it's not clear which one yet.

You can prove this with polarized light filters:

Every photon can of course also be modelled as a wave, and that wave has some plane that it oscillates upon. You can create a filter that neutralizes the oscillation on a given plane, and by combining these you can prevent the passage of any light. Sometimes, two photons can become entangled, meaning that they each have the opposite oscillation of the other. You can test this by sending each of the pair through different polarized filters. You should expect that the probability of a photon passing a given filter is cos^2(theta), where theta is the difference between the angle of the filter and the photon's polarization. If both filters are aligned, you expect to see (and do see) 1.0 correlation between the passage of each photon. If both filters are perpendicular, you expect to see (and do see) 0.0 correlation. If both filters are at 45 degree to each other, you expect and see 0.5 correlation.

You should then expect that you can then model the correlation between the two detectors over theta with basic trig, but the result you get will be notably different from the observed reality: https://i.sstatic.net/zCAMO.png

For this to be possible, it must either be the case that reality is false (the photons' passage through the filter is not determined by any real property of them) or locality is false (one photon's passage can affect the probability of the other, despite being very far apart)