the variable %s is not resolved in a single journal installaiton (OJS 3.1.1-4). I ported the code from OJS 3.1.2, so maybe it works in OJS 3.1.2.
But I looked at the code and the variable s is resolved with the site name. In our single journal installations there is no site name though.
Is it possible to use the journal initials or journal abbreviation in these cases? Journal titles may be quiet long.