How to get best conversion results and playback quality of wavetables?

[Frankbeat]

I did a test: Loaded an almost perfectly band limited square wave cycle (44100Hz/32Bit, duration: 1800 samples) into a sampler, rooted at G0 and spread up until G4 – Convert samplemap to Wavetable Bank with these settings:

Then I loaded its output file (_Left) into a Wavetable Synthesizer (HQ enabled). Somehow, as .hwt my root note now is exactly one octave higher (900 samples) – no problem I couldn't fix but: Aliasing is introduced by this process:

This is what the edges of my prototype looked like:

What can I do about that? Would it require an oversampler to get cleaner results?