Yes, this. Of all the things I learned in SR, the example of two particles of the same charge approaching one another near c and the force vectors not lining up

Yes, this. Of all the things I learned in SR, the example of two particles of the same charge approaching one another near c and the force vectors not lining up with the line between them was the most mind blowing. Instantaneously, conservation laws were violated, they held only over a “long enough” consideration of the interaction. Newtonian mechanics is a useful approximation at certain scales. At other scales, they are problematic.