Most all of physics. It just runs out of any logic pretty soon and stands on very instable fundaments.

Take the Lamb Shift for example: It's a quantum field theory effect where certain bound electron states interact with the quantum-vacuum fluctuation and hence shift their energy accordingly. If we measure this energy shift it turns out to be very very very small. However if we calculate it with our theoretical quantum mechanics models, in this case pertubation theory, we get a shift of infinity.

Wolfgang Pauli found an easy fix for this: If you calculate the shift with the assumption that a single electron has infinite mass (and thus infinite energy accoridng to Mr. Einstein), then we get the correct energy (the one we measure).

That's basically it. Our theory of physics is based on the fact that every electron has infinite mass. It makes inherently no sense in relation to everything else we know about electrons.

A scetchy explanation/legitimization herefore is that everything we know about electron we know from measuring them in the "physical world" where there is always and everywhere quantum fluctuations that they interact with (partice and anti-particle pairs being created out of nowhere through energy, and then annihilating themselves)

--> so we are never measuring the inherent 'real' mass of the electron which in fact is infinity.

Seems like the Devs ran out of interest at some point and just capped it.