illustrator ver 23.1.1
os ver macos 10.13.6
16gb 2.8ghz hd5750gpu board.

While working with illustrator (2018-2019 both are doing the same thing. While moving or duplicating curved objects around the page, or while saving the document, it's randomly picks a one of curve nodes and elongates them to random length. Done experimenting with other mac stations and same file, we cannot reproduce this behaviour. Uninstalled - reinstalled illustrator and updated os system didnt help either.