If I understand your repro steps correctly, this is essentially what you have done, except for the fact that you are working in a bigger (non-test) project and have previously made changes to the Micro Dragon blueprint other than changing the mesh and animBP.
You mentioned having parent and child blueprints. Is it Animation blueprints that are inheriting from a parent Animation Blueprint? Or is it just regular blueprints inheriting from a parent blueprint? Regarding the logs, I believe TRASHCLASS and “ClassGeneratedBy is null” are the key points to raise eyebrows. These generally indicate that the child has a missing reference to a parent. I would suggest re-creating the parent blueprint (or animation blueprint) from the ground up and as you make changes to the parent and/or child, test for compiler crashes.
I know you said you have a slow upload speed, but it’s hard to picture exactly what’s going on without having the project in front of me. You’re welcome to PM me with a link to your project if you’d like me to take a closer look.
Hope this helps!
-Jake C.