Rendering messes up all clips

Please help! I am creating a music video with lots of quick back and forth clips. It looks great in my Rush window, but when I export it, almost all the clips are completely shifted to include pieces I deleted, and the whole video gets messed up. Is this a syncing issue, like I'm not keeping the files in the sequence long enough to let them sync before I start trimming them? Or due to my using an old laptop (which created video files from Rush a few weeks ago with no issues) and using many quick clips? The entire video is only about 3 minutes long.