Accent height above note when bulk copying and pasting sometimes is too high/not right above note or previous articulation/ornament

In order to investigate we would need you to attach your score and give steps to reproduce the problem. Most likely there is some other element underneath preventing the accent from moving down, you'd have to disable autoplace for one or the other.

Accent height are indeed not right for me too when space is missing above the note. See attached file, the clarinette part. Accents are a mess and cannot be moved to the right spot.

To mitigate this, you have to manually stretch the measure both in the main score and in the parts (modifying the main score alone won't do it for the parts) which is a pain.

You have far too many measures on a staff in the part. You need to spread it out a little to make it easier to read anyway. I quickly added some system breaks to the score to avoid ugly stair step accents.