I initially rejected the hint that a child born in 1879 died in 1878 but went back to it after finding 17 trees show it happened. There's no way they can all be wrong and just little old me be right 
Oh it can! years ago, I rather naively sent my tree to someone, very distantly related who then shared it over and over on Ancestry. I then found an error in my tree and corrected my mistake but all the shares still have the error, an additional child (baptised but no birth record, went back to my original records I transcribed at the RO to double check and it wasn’t there so I must have been seeing things at the time! 😵💫) Not one of the copied trees checked my records
I've built the trees of several mystery matches and shown my grandmother is an NPE but my known matches don't research, they just copy the crowd and think they are descendants of William the Conqueror, Robert the Bruce and King Arthur. Strangely none of those are in my tree though my grandmother is the MRCA we all share.