I dont play much survival mode, but I have gotten to at least round 10 on every map except hardhat. However I have the Survivor trophy which requires you to reach wave 10 in each survival mode mission. Is this just a flaw or what?
This happened to me for the wave-15-on-each-map trophy. I got 15 on all of them but one, and then I played a map that I had already gotten to 15 on, got past 15 on it again and the trophy popped up. Checked back to make sure I didn't have 15 on all of them, and I didn't.
I think it's just a glitch.