I needed to redirect the user after form has been submitted, so logical way to get that done was to add sc_redir(""); in to OnAfterUpdate action.
This does work however redirection happens before form changes are saved, despite being in an action that should happen after update took place.
This looks broken to me, as I expect OnAfterUpdate to execute after record has been updated in the database.
At the moment my solution has been to use ajax to update the form and bypass built in update button altogether.