To to reproduce the issue I’m seeing here these are the parameters:
HS SE Basic library
[GM 41] Violin
Play a sustained note at g3 then notice a high harmonic begin slightly after the note starts playing.
This happens a little with A3 and B3 but it is strongest with G3.
It doesn’t seem to happen for any other notes. My theory is that there’s some resonance related to the built-in vibrato or some other detail, but I’m not able to get this harmonic to disappear.