DNA I manage has hundreds of matches showing as maternal

[hurworth]

Someone told me today that her mother was given over as a baby to the birth mothers brother + sister in law to raise

In  this case if the descendants didn't know the story all DNA matches would connect to father's side and none to the mother unless the connection was farther back .

Which made me think of your scenario . I wonder if it could be something like that .

* If the "grandmother " (fathers mother)  had a late baby that the young couple took on that would explain why seemingly paternal matches all come out as maternal .

The father's mother is his PATERNAL grandmother, so would is still a paternal connection. 

[hurworth]

How much DNA does he share with the first match that you think is paternal, but Ancestry is assigning them as maternal?

[brigidmac]

You are correct Hurworth

In my scenarios the matches would actually be maternal to the actual  birth mother (from legal fathers side )

But ancestry would automatically allocated  to whichever side the tree owner had allocated as paternal .

So unless as previously suggested the tree owner & DNA testee had put the wrong generation home person  it would not explain this case .

Penelopej will have to get back to us .
It could be useful for other people.