If there is a Smalltalk process currently in external code, the image cannot be saved cleanly!
Whilst the tag whether the process is in external code is saved, the context of the external code cannot be saved.
Therefore if such an image is loaded the Process is blocked and can never return again.
Possible solutions:
When coming up on reload, call the primitive again with the same arguments.
Fail the primitives that are currently in external code when coming up on reload.
Fail the saving primitive if there's still an external process running.