This is first-line pitch instability — Suno hasn't 'found' the singer's range yet when the vocal enters, so the opening line can shoot up an octave or come out squeaky. The rest is normal because the voice locks in after that.
1. Don't open on a high note. If your first line sits high, rewrite the opening to start mid-range and let the melody climb later. Suno follows the contour you imply.
2. Anchor the voice first. Add to Style: warm natural female vocal, comfortable mid-range, no falsetto. Giving it a register to live in prevents the opening spike.
3. Start with a soft entry. [Verse 1: gentle soft vocal entry, warm] — a soft opening gives the model room to settle instead of belting the first syllable into chipmunk territory.
4. Replace just the first line. If the song is otherwise perfect, use Replace Section on the opening line with the same lyric and [warm natural vocal, mid-range]. Five-minute fix.
5. Regen is cheap here. First-line chipmunk is random — the same prompt will often come back clean on the next try. If two in a row do it, then change the opening line's pitch.
Good luck! Hank founder of SonorixPG