Can't save Sequence... external private object?!?!

Development Cinematics & Media
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How can I diagnose this problem? I create sequence A, save it, ok. I create sequence B, save it, ok. I create sequence C, save it, ok. I go back to seq B, try to save it, error!

Can't save [path][Seq B].uasset: Graph is Linked to external private object MovieScene [path][seq C]:[seq C]:MovieScene_0 (ControlRig)

Why is SeqB bothered by SeqC?!? They’re not embedded or anything.
Why does it say “(ControlRig)”?

Unreal Engine 5.3.2, Windows…

Possibly relevant: I initially dragged a raw control rig asset into the scene and the sequence (ew!), then later, realizing that’s not how you use control rigs, deleted it from the sequence and the scene (in that order!). Replaced it with a blueprint holding both the skeletal mesh and its control rig.

So maybe it’s a bad reference that’s sticking around? BUT this infects sequences that had been saving ok previously! :rage: and this problem is now occurring when I make a completely new map, new sequences, using the same assets. :sob: (Which behave OK in other maps & sequnces–they are not universally bad)

I see from a fair bit of searching the forums that 'cant save... external private object' is a common and hard-to-solve problem. And this version really sucks, because i have to recreate a lot of parts before the problem appears :face_with_symbols_over_mouth:

Please, how do I investigate this?
I have tried “Clean Up Redirectors”… what else can I try?
This bug is devouring my project!

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Update: following a clue from this post, I tested the following:

build new map,
add my blueprint (contains skeletal mesh and control rig)
create seq a, add the BP to the seq, key its ctrl rig, save it
create seq b, add the BP to the seq, key its ctrl rig, save it
return to seq A, save it, BINGO!
Can't save [seq]: Graph is linked to external private object MovieScene [etc]

I remove that BP from the sequence, and it can save without a problem.

I tried this with a differnet blueprint (also SKmesh + ctrl rig) and had the same problem. I tried it with the Animation BP Manny and did not have the problem, but that’s an Animation BP.

I built these blueprints following the directions in “Control Rig Component” so I think I’m following best practices. These are simple vehicles, not full-blown characters. But assets created in this way cause an error if they are used in two different sequences from the same scene.

Workaround for now: do all animation for this blueprint in a single, long, subsequence that can be referenced by the ‘master’ sequences. I have tested this approach and it does not cause the error. (Or I could just do all the shots together in one maxi-sequence.)