29th: When NOT to believe certificates?

Seem mostly to be dna-ing of late, trying to figure out how on earth the matched FAIRBAIRN families are likely to connect.
As a result of a lot more digging around in the OPRs, earlier parts of trees, and old mysteries. On the latter, I have bitten the bullet and decided that despite what two certificates say, the John FAIRBAIRN of Stillwater just has to be the son of David and Jane (WILLIAMSON) FAIRBAIRN.
This John is the chap whose descendant Walter claimed to be a cousin to his wife Clarissa, a descendant of David and Charity FAIRBAIRN, His marriage cert stated his father was Johnathan, and his death cert. gave his parents as John and Agnes (WILLIAMSON) FAIRBAIRN, and he was most unhelpful in that I don't think any two records over his life gave consistent birth years and places, with his birth year ranging from c 1833 thru to 1841. I've documented my conclusions and reasoning on his newly created web page.
The FAIRBAIRN introductory page has had a bit of a revamp, reorder, and some more charts included (some descendants of the dna matched families).
Check the FAIRBAIRN DNA Project Diary for what changed as far as dna pages go.