Duplicate contacts can not be found due to apostrophes

I just merged a lot of duplicates on my mothers iphone to help her sort out some of the mess she is having with way too many of the same contacts. Now it became a little better (used some apps), but there are still lots ⚠ of duplicates. Problem is, the name is first displayed normally, like Tom Smith, and then the same name, but covered with apostrophes ('Tom Smith'). This means that the apps that deal with merging duplicates cannot read them as duplicates. Or maybe they can? Is there in any case some way around this problem, and still possible to cope with this duplicate-like problem? 😕