I’m just a happy user.
In Anki you create NOTES. According to rules you set in the card templates window Anki automatically generates CARDS from your notes. You review these CARDS. These cards only hold scheduling information and no content.
You can’t delete single cards. You can delete individual notes. Then all the cards that are generated from them are removed. This explains “If I try to delete one of the duplicates, both of them get removed.”
You can also remove a card template so that for all notes of a certain note type the “card 2” is deleted.
It seems that you want the latter. You seem to have somehow misconfigured the card templates for the IO note type.
Distinguishing between notes and cards might seem complicated at first but it’s a really powerful mechanism that can save you a lot of time in the long run.
for details see e.g. https://docs.ankiweb.net/#/getting-started?id=key-concepts
If you don’t like the manual there are also many good videos about anki on youtube, e.g. for the difference between notes and cards there’s https://www.youtube.com/watch?v=5ZdMAePorUI
If you can’t solve the problem with this info you might consider reposting in the official IO support thread where the add-on creator gets notified about your messages, Image Occlusion Enhanced [Official Support Thread] It’s likely that he’ll miss this thread.