Since you’ve posted in the Sony Software forum, I am assuming you are editing in some version of Vegas.
I’ve never encountered this particular problem and I routinely do multi-cam editing saved as an .AVI file. But if I encountered this problem, I’d try doing a pre-render of the area in question to be certain it remains in synch on the timeline. Then render the file again as an .AVI and see if the section you pre-rendered remained in synch.
I do seem to recall that something similar happened to someone a while back. And several individuals responded with suggestions. Perhpas you may want to add a few details like, your NLE version, perhaps results from another format, how many frames out of synch is it (load the rendered .AVI into your NLE and it is easier to work out,) and to save time, just select a loop around your spot & render just the loop region. And then post again, but in general post-production.
Good luck, who knows maybe the pre-render will help. I sure hope so!
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