I don't know, if this is already reported, I searched, but haven't found any task, so I hope I haven't overloocked something :)
If I try to add a new sitelink to Wikidata in beta labs (e.g. to http://wikidata.beta.wmflabs.org/wiki/Q70055) it will be added, but the View will always show "saving". The console gives me:
Uncaught TypeError: Cannot read property 'title' of undefined(anonymous function) @ VM214:616jQuery.Callbacks.fire @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:45jQuery.Callbacks.self.fireWith @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:46jQuery.extend.Deferred.jQuery.each.deferred.(anonymous function) @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:47jQuery.Callbacks.fire @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:45jQuery.Callbacks.self.fireWith @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:46(anonymous function) @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:47jQuery.Callbacks.fire @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:45jQuery.Callbacks.self.fireWith @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:46jQuery.extend.Deferred.jQuery.each.deferred.(anonymous function) @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:47(anonymous function) @ VM214:454jQuery.Callbacks.fire @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:45jQuery.Callbacks.self.fireWith @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:46done @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:135jQuery.ajaxTransport.send.callback @ load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=1KfMGVrs:141
The api result returned:
{"entity":{"sitelinks":[{"site":"dewiki","title":"Testlange","badges":[],"url":"http://de.wikipedia.beta.wmflabs.org/wiki/Testlange"}],"id":"Q70055","type":"item","lastrevid":217166},"success":1}
I think the problem is, that you try to search for the wikiid (e.g. dewiki) in an array, which key's are numbers (0,1,2,3...). Haven't tried that in Wikidata production, because I don't want to add and remove pointless connections between wikidata items and real wiki pages :)