So server image was saved with running server, right?
And actually it was saved with connected client. Error shows that after image was saved communication with client was continued. But when server restarts client is not connected to it and server signal timeout because no connection is available.
How you saved image?
Doing it from remote playground will lead to such problem because evaluation expects result from server. And after restart server will try return it again.
To correctly save image evaluate "remotePharo saveImage" from local playground. It take care about such cases (it request server without waiting result).