Right. Originally QM Theory was only valid for low energy/speed situations. But already in element spectra, there was a problem with matching prediction with measurement. The electrons were moving at relatively high energy/speed. So for elements heavier than Hydrogen, the electrons are more energetically bound by the larger number of protons (which determines element, not isotope). The higher the energy, the more particle-like the phenomena is. In ordinary light, the energy isn't so high, so waves are a good description. With more energetic EM waves, say gamma rays, particles are a better description. But already the particle aspect was detected in the photoelectric effect, as explained by young Einstein.

Later, with Dirac, an explanation was found that applies to fermions (electrons) ... the Dirac Equation. The slightly earlier Klein-Jordan equation is for high energy bosons. This made QM Theory even more confusing than it was already. But it did explain the spin of the electron, magnetic field of the electron, and predicted the existence of antimatter (positrons). Applying the Dirac equation to the field, not just the particles, was even worse. This took until 20 years later, to explain (Feynman etc). The first Standard Theory is Quantum Electrodynamics. Later the Weak Force and the Strong Force were explained similarly. This brings us up to the present version of the Standard Theory.

So ... the current version of the Relativity/QM problem is ... reconciling the unobserved graviton (but we have detected gravity waves) and the observed Higgs boson. And there may be more than one Higgs boson in some extensions of the Standard Theory. It takes colliding neutron stars to detect gravity waves ... it takes even higher energy to produce gravitons. Again, given non-free energy, generating a single graviton, even if they exist, takes a cosmic amount of money. BTW - tachyons are theoretical particles that ONLY move faster than light. These seem to be ruled out in nature ... also magnetic monopoles seem to be ruled out (a N field by itself, or a S field by itself). Other exotic theoretical particles have been devised.

The teleportation issue ... is related to the notion as to what identity is. Is there one identity for two people who are even closer than identical twins? Depends on if materialism is correct. I am not a materialist, so teleportation would be a special case of murder. There is no necessity, if you have teleportation, that the original needs to be deleted, in fact, the buffer of data can be used to make many copies of you. And of course, that would be a Star Trek version of the Clone Wars in Star Wars. One could generate many thousands of copies of Commander Spock. No wonder Dr McCoy didn't like teleportation!