Zone Plate Reconstruction
Lanczos2 has a frequency response peak of about -40 dB or 0.01 at about 0.9 times the sampling frequency, see this question. Your peak aliasing outside the main lobe is just left from where the aliasing goes to zero frequency so I think it is the same peak. The amplitude of the aliasing is also roughly as expected.

So I don't see any error by you.