Here's scenario A (sampling at the zero crossing point): -
Image from here.
Based on the samples taken, you'd estimate that there was no signal and that ties in with this: -
at the exact Nyquist frequency, 50 kHz, the amplitude is heavily reduced
On the other hand, if the samples happened to be offset by 90° you'd conclude that the amplitude was correct.
there seems to be a DC component
Your image shows nothing but, with some waveforms there might be or, it might just be a residual DC value.
What is failing in the theoretical Nyquist theorem.
Nothing as far as I can see.