If you copy a solid from one project and paste it into a different project, instead of properly pasting it, it creates a layer with source name "Original Source Deleted" instead, with a colour bars icon on the left. You can't go to the solid settings or anything. Surely this is a bug.
Well, that's because you CAN'T copy a solid from one project to another. You have to import the project with the desired solid into another project.
I'll guess there's more to this, like the desired solid moves in some special way or has just the right combination of effects.
Otherwise, any dolt would just make a new solid.