Replying to Dropped Frames in FCP

Are very annoying. I have tried many things to fix it but nothing works. I'm using footage from a 960 go pro, HD go pro (filmed in 720 at 60fps), and a 7d. I've made all the clips the same, apple pro res 422, 29.97 and 960 x 720. I converted the song im using to AIFF. Yet, i still get the pop up saying it has dropped frames. Some clips will play fine, but others drop frames. I'm still new to FCP, so it could just be my lack of knowledge.

I started a new project and tried playing the clips without the song, which so far has been working. But when I put the song in, I get the message again.

Any help would be very appreciated.

Thanks