THe answer was given by the Jurre and I've added it here so that the question is marked as answered and can be closed:
We have found that there is a unicode character when you copy from iPhone contacts. This was not filtered beforehand even when we trimmed. https://stackoverflow.com/questions/47623828/ios-copy-paste-phone-from-contacts-to-uitextfield-adds-strange-unicode-character We now replace all unicode by using replaceAll(attribute,'\p{Cf}','') You actually can see the unicode in the modeler, but it won't show in any browers or such.
Not completely proficient in regex statements, but I can't get a phonenumber to match your regex.
But give this regex, for dutch phonenumbers, a try in your regex tester en the split to see if there is a difference.
(|(^\+)[0-9]{2}|^\+[0-9]{2}\(0\)|^\(\+[0-9]{2}\)\(0\)|^00[0-9]{2}|^0)([0-9]{9}$|[0-9\-\s]{10}$)
Maybe this will give you a clue on the issue with your regex statement.