LFO speed Sample scanner warble

I couldn’t find an answer to this so here we go: I was experimenting with loading a long sample into the sample scanner and modulating the position with an aliasing saw wave at low speeds. The goal is not to do wave shaping but to play back the original sample (opening up the possibility for phase modulation). The only problem is that whenever I have the saw wave at low frequencies, it seems to make the pitch of the sample drift up and down, as if the playback speed is shifting slightly due to a slightly kinked saw wave. I noticed the same thing happen with the aliasing triangle. I know this isn’t the intended use of this unit, but am I missing something?