I think this is one of the biggest challenges for Ancestry in finding common ancestors and not sure how it can be addressed. For example, I have one match who's gone wrong with their grandmother (just say she was) called Ethel Bloggs born in Worcs, but my match has picked up another one born in Sheffield. The former isn't in my line, the latter is, and so Ancestry picks up a common ancestor when there isn't one. Our real common ancestors are on another line but Ancestry can't see this. Their new format, apparently still in Beta test, might get round this as it shows multiple connection options.
There are so many simple mistakes in trees (we're all fallable) that make it difficult to find the connection, although perhaps that's part of the challenge. It would be nice if people were more open to being challenged on info in their trees but there are many posts on here about rude reactions to trying to help - how very dare you and so on. And it cuts the other way. I had a stiff lecture from one match about my own line and, when I provided the evidence to support my tree, they refused to engage any further.
At least your own match was willing to review their work, which is nice.