There's no error message for this, because Avid doesn't like to admit when it's just fucking wrong. Also, this is almost certainly related to the issue with autosequencing that I raised in my Avid Behaving Badly #12 post below.
Here's the bullshit workflow we have to use because stupid fucking Avid can't play back proxy MPEG-4 video in 9 camera split without stuttering (I know, it's not an every-frame-keyframe codec, but jesus christ, maybe if you used more than 2 fucking cores of my SIXTEEN CORE system, you'd get, I don't know, more fucking processing power!! Seriously). First, we capture using AI direct because Avid can't be bothered to implement their own tapeless fucking workflow. Then we have to transcode everything to 8:1m because that's the only codec that works cleanly in 9 cam multicam split playback. Transcoding, by the way, takes for goddamn ever. I'm sure you knew that.
In order to transcode to 8:1m, for some reason that makes no sense whatsoever, you have to be in an NTSC 23.976 project. Nevermind that Avid's entire workflow is based around digitizing all of your footage in low res and then uprezzing later to HD. No, Avid doesn't give a fuck. So it forces you to use what it calls a standard def "23.976" project. But there's one problem with that: There is no such thing, according to Avid, as a standard def 23.976 project! What? That's right. Once you go to standard def, even though Avid displays that you're in a 23.976 project, you're actually in a 29.97 project where the timecode is being pulled down to 23.976. Which means timecodes get fucked up all the goddamn time.
And that, dear reader, brings me to this issue. Let's say that you realize, while in this "standard def" project for your transcode, that one of your tapes was accidentally mislabeled when you digitized it. Maybe you fat-fingered it to have an extra 0 in the name or something. Happens all the time; honest mistake. So you go to modify the clip and change the source to the correct tape name. Except, after you do that, your clip changes in duration from 1:14:05 to 1:30:12. WHAT THE FUCK? And then if you load that clip and go frame by frame, the frames will count like this:
HOLY WHAT? God damn, Avid, WHY DID YOU DECIDE TO FUCK ME TODAY???
And here's the best part: Your clip is now fucked for good. You have delete the clip, delete the media, and re-ingest. All because Avid insists that standard def 23.976 is somehow different from a low res version of a 1080P 23.976 project.
Fuck you, Avid.