How was the user account deleted?
If an account is unenrolled from its Editor enrollment, but the account itself (email, username, etc.) continues to exist in the system, there should be no change in the operation of the system -- just that the user will no longer be able to access Editor elements of the system.
If an account is deleted entirely, by the use of the "Merge Users" feature, all of the user's "assets" (editorial assignments, reviews completed, etc.) will be reassigned to another user as selected during the Merge process. I don't recommend doing this because it alters the record-keeping of the system. It also shouldn't cause other users to have trouble continuing the workflow on those submissions.
I'm not sure how either of these approaches could cause a submission to be stuck for other Editors -- is it still around to perform some debugging on?
Public Knowledge Project Team