Einstein’s theory often predate quantum mechanics and thusly quantum mechanics will cause "discrepancies" with standard Einsteinion physics. And thus very small amounts of matter and/or energy may react in very odd ways, see Schrodinger's cat. Also in the most extreme situations of quantum mechanics cause and effect are not clear and it can appear that cause fallows effect.
On the bulletin board in our university computer lab was an article that reported the evaluation of the speed characteristics of a new type of transistor logic. (This was in the 1960s, mind you, when you had to submit everything on punched cards and get the results back the next day on wide printout paper.)
They discovered that over a certain range, the propagation time through a basic gate was an inverse function of the supply voltage. This was shown in a graph.
They then extrapolated to a much higher supply voltage, at which time the prop time was extrapolated to go to zero, and then negative.
They reported that they measured the logic at this new, much higher, supply voltage level, and began to see output states on the test gates that could not be correlated with any stimuli except those which they were about to apply.
And the gap continued to widen. Pretty soon, they were getting outputs from the test gates from inputs that were to be applied the next day.
Things continued to get more confusing for weeks, until they finally received printouts in their inboxes that were undecipherable, until they realized that these were from programs that were yet to be written, on a machine that was yet to be built, using their newfound ultraspeed logic.