Cathedral fetch and clear high level

[Ripper1302x]

I have twice failed to complete a level IV fetch and clear mission to the cathedral/church. I have no problem with the fetch but can't get the building cleared. I think I know the building well because I visit it when looking for books and always search the coffins in the basement, and the good loot in the two towers, and clear the vultures from the large roof area.
What specific part of the this large stone church might I have overlooked or where there might be a hold out zombie hiding? BTW I only get red dots about 1/2 the time when clearing this building.

[Shurenai]

Mmm.. From my memory of the church, the only places I can think of where you wouldn't immediately stumble into the zombies you need to kill is in the stairwells; At least one of them goes both up -and- down; and zombies can spawn in both directions. Also i believe a total of 3 vultures spawn up top, so make sure you get all 3 of them as they Are counted in the kill requirements.

[oohbetty]

theres some confession rooms at the front of the main chamber, and did you get the birds at top of the tower, failing that try running around hitting things to stir any sleepers etc, lots of noise sometimes helps.

[comet_65cali]

Make sure you check your compass. There will be yellow dots to areas where you need to go. When you are in that particular area, you will see red-dots for the locations of zombies you need to clear.