While searching I discovered that a portion of the Pushlinch Division of Wellington County Records for Canada West are mis identified as being part of the Brock Division of Ontario County.
The original enumerator did not fill in the County & division at the top of the folios but identified them as "Puslinch Division 2 / East Side Brock Road" - images 1 through 56 in http://search.ancestry.ca/Browse/View.aspx?dbid=1061&pat...
are affected. If you go to library & archives Canada and compare the images to RG31, Reel C-11743 (Found by searching Canada West, Wellington & Puslinch) they are identical.
I have posted to the support form using the "Contact Us" link but this seems oriented towards end-user issues rather than issues with Ancestry's Collections.