Multiple Custom Fields

When I add 2 custom fields with the same key all links in my post change to start off with the post name. Also if there is a ‘ in the post of title a / appear before it. I have tried editing the links to get rid of these but the bug comes right back, even if I delete the custom fields. Is this a bug, or is there some other way to one only use 1 custom field to get the same results as 2 custom fields without these results.