I stumbled across this video from a series called "Setting the record straight".
This episode talks about misinformation in online family trees and how errors arising from copying the incorrect information occurred long before the advent of the Internet.
https://www.youtube.com/watch?v=rIOcGzdhmUc
The example he gives resonates with me.
For a long time, many trees (pre-Internet) allocated the incorrect parents to my 5x-great-grandfather, Thomas Quintrell. Another researcher and I almost simultaneously discovered the truth. The Thomas Quintrell whose baptism this assumption had been based on was buried shortly after his birth. Nobody had noticed this mistake and the incorrect information spread amongst Quintrell descendants.
We were then able to ascertain that the parents of our Thomas were Edward and Mary and were not at Edward's home parish of Gerrans but at St Agnes (Cornwall). The family later returned to Gerrans. Our Thomas indeed had children of his own named Edward and Mary.
Many incorrect trees still exist.
There is a series of videos that I might watch.