Problem with BP fron actor on Datasmith in UE 4.20

Hi !

I have a little(big) problem with Datasmith in UE_4.20.

I export my project from 3ds max, import in UE with Datasmith plugin. Ok
I make some change in object properties.
-Save level- OK

I create BP from actor on the Datamith (like doors), but when I place it in the level, it’s impossible to save.
With this warning Message:

Can’t save ./././…umap
Graph is linked to private object(s) in an ecternal package.
External Object(s):


When I delete the BP from the level, I can save again.

I have not this Pb in UE_4.19

An idea to solve it ?