Stretch causing clicks and Inaccurate waveform

[Glubber]

Step 1) Import sine.wav file to empty track.
Step 2) Split item at zero-crossing.
Step 3) Slightly time-stretch the left half of item, using left edge.



Result (above): Audible click at split point, even though wave form looks perfect.

Step 4) Glue 2 items back together.
Result: The waveform updates to show the cause of clicking:



I tried all the different stretch algorithms in Project Settings, same result. Is this inevitable, because play-rate must change in order to stretch? When I try a similar process using stretch markers instead of splitting the item, I get similar artifacts. I have selected "Tonal-optimize" under Project settings. Crossfading doesn't fix this. Forgive my ignorance.