I've been having some issues with syncing externally recorded sound on 4k footage in a 1080p project. So far most footage was shot in 1080p and I had no trouble with my standard routine of exporting to plural eyes, reimporting to MC, making subclips, autosyncing and cutting the synced clips back into the sequence. Now I was confronted with some 4k footage which had already been ingested via AMA-link and transcoded (project settings changed to UHD25p) and initially, I wasn't able to autosync, because MC told me there was an effect on the video track (frameflex). I managed to work around this issue by changing the project settings back to UHD25p, making a subclip, autosyncing and cutting the synced clip back into the sequence - everything fine up to this point.
We then went about our usual business of organizing footage into new sequences by themes and unfortunately I didn't have all of my waveforms turned on, so it wasn't until later that I realized when I cut these 4k synced clips into new sequences there was no more sound on A5 (the externally recorded track) i.e. the waveform was flat. I checked back in the original sequence and the synced clips themselves, and the sound is there. Why can't I move that to a new sequence? I've tried in both 1080p and UHD25p project settings, but that made no difference - A5 is always mute. I've uploaded three screenshots of the problem for better understanding.
We're editing on MC 8.5.3 on an iMac running OS 10.10.5 Yosemite.
I'd be extremely grateful for any advice! Thanks a lot!