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.)