To properly configure for the GT S-Series Stator, you’re gonna have to re-detect the FOC parameters for that motor, since it’s fairly different from a standard GT, which the GTV is tuned for. First, make sure if you haven’t that you have a Backup of the starting configs (can make backup under the Start tab), so you can revert if you mess something up.
Go to Motor CFG → FOC → General, then tap the “…” in bottom right. Tap “Detect FOC Parameters” and run the full sequence (there’s two buttons for the two different steps). Once done, tap Apply, then tap Write at the bottom (Apply does not write to the board, it just fills in the values). If your observer gain was detected above 1.0, I would probably cut it in half and Write as well. Then go to “…” again, tap FOC Hall Detection, and run that as well. Again, Apply, then Write.
And hopefully that should run better. If it does, feel free to make a new Backup.