Merge Three Episodes of Series

I tried to create the an episode of a series several times (thinking the other attempts failed) and ended up with three entries for the exact same episode. I thought I could merge (they have the exact same title and exact same release date) but can't make it work. There should only be one single episode called "XYZ". Curretly there are XYZ (I) XYZ (II) XYZ (III) How can I fix this? I submitted a merge request and received the answer that I can (and should) merge the titles. When I click the "edit" button at the bottom of the page I can't find a way to merge episodes. Other Corrections => Episode Title / Number doesnt' give me a merge option.