How many of us have been tripped up when doing family research? The first rule should be, check the original documents. The second rule should be, don't quote family information you haven't checked.
And some people do. I'll never forget the gentleman I sat next to in the library one day. He said, "Ah hah, found them!" He explained that he'd been visiting relatives and they'd given him information which he was now checking to see if their data was on the bdm indexes. (Before bdm nz was online.)
Another story I heard (very second hand), was that of a lady at the GRO in London found crying. It turned out she had been researching the wrong family for five years after assuming some information found in her earlier research days was correct.
Families can sometimes defy logic. I have one family which named two surviving daughters Isabella with a slight differentiation. Another family was complicated by their being two instances of the same combination of names in the same locality, one not being family at all.
I've made assumptions too. What dear old such and such says must be true because it fits. But the real facts were much more interesting as it turned out. I've been embarrassed at my own naivety. However, I've learnt that I can admit when I'm wrong and carry on after the deflated feeling goes away.