Hi, this has been an issue in Maya for years, and it is extremely frustrating when dealing with organized node graphs. Pin all nodes by default is a frustrating work around and often riggers forget to enable it, or some nodes don't get pinned before enabling the option.
This most often happens when a new node is created when you connect 2 attributes. Like when a unit conversion node is made.
Video demonstration:
https://www.youtube.com/watch?v=aCQYjcWk_CQ