Matching Bug
First we suspected a bu with safari. Finally we found a general problem in the matching view. Thanx @dodis for reporting.
If a user try to match a wrong concordance (f.e. provider A + provider A), the action Actions.MERGE in concordance store fails. Because of the failure the edit_list doesn't clear. If the user then continue to match he/she still has the old edit_list in the local store. So the next match will fail, because there are still the wrong data in the edit_list.