Alright so I'm working with a Canon DSLR and a zoom H4n. I've done this many times.
I bring my Camera video/audio into the viewer find a sync point mark it and drag into the time line.
I then find my audio file put it in the viewer find the same sync point, mark it and drag it into the timeline.
I then match the two marked points and check to make sure the two audio files are in sync (no echo).
I then unlink the original audio from the video and delete it.
I link the video now to the H4n audio with command l. I do this with all my clips then drag them into a new bin usually called synced.
At the moment I'm working with interview footage that's one long audio take and one long video take. I've sunk them in the manner above. I now take the synced up video from the synced folder and open it in the viewer. Everything looks fine. I subclip the various parts of the interview using in's, out's then command U then rename them in the bin needed. When I go back to look at them in the timeline by dragging the newly named subclips from the bin they are completely out of sync buy 10's of seconds.
I've never had this happen before and have no clue why. Any thoughts