I, too, encountered the same problem in the Caen campaign. I hunted down all the scattered German crews and wiped them out, but still could not get a win. Ultimately, I found one group of German infrantry just off the playable area of the map that - for whatever reason - would not enter the map. As soon as I started firing on them, they hit the dirt and I could not flush them. Try to call in my last remaining air strike, but to no avail.