Multiclip shifts frames that were correct in timeline

Hi All,
I am trying to create a multiclip with FCP 7. I had originally multi clipped all these clips through the browser, and they worked perfectly. Then we discovered that there was an issue with our audio channels, so I reconnected the media to the proper clips (the exact same codec, frame rate and length) with the proper audio we need. Now I have gone into my browser with the new main clip (with the audio) and the same B cam as before. When I place them on the timeline and sync the audio, everything stays in sync from beginning to end. But when I create a multi-cam clip through the browser/modify/make multiclip selection, my video for my b cam is about 5-10 frames off. I have been measuring out the exact frame that the in or out points fall on for each clip and making sure I am very precise on the measurements of the clips before I create a multiclip and yet somehow the video for the B cam is still off. I am doing it the exact same way as I was before with the original media and the multi cam clips were working perfectly. I know my files are in the same formats and the frame rate is the same. I cannot figure out what the deal is and why my multiclips won't line up correctly!! Can anyone help me? Thank you so much in advance!

Best,
Lauren

What codec are you using?