Replying to Premiere pro export help

Ok I'm having some export issues in premiere pro cs6. I shot the edit with a combination of 24fps and 60fps clips. The sequence settings are 720p/60fps, and I'm trying to export it as h.264 with a 24 frame rate. At first the 24fps clips looked very choppy, almost like a stop motion, so I exported it again and a couple of the 24 clips looked fine, but then I noticed one of the 60fps clips was all choppy too. What the fuck is going on? Please help, 10/10 for helpers