@DrewSSP ~ I did a lot of testing on this, and I basically came to a few conclusions:
Phantom entries are created when entries are deleted from the database AFTER they have already been tested on (but I knew that already from when I first encountered them a long, long time ago). It was very easy to create them during my testing.
They are not created when columns in a database entry are changed in some fashion, even if they have already been tested on.
They appear in both the web version and the app version (at least the iOS app, as I didn’t verify the Android version).
They appear regardless of the number of columns in a database (I tried between 2 and 6, and even a test case using an image-based column).
The key seems to be WHEN the database row was deleted. BEFORE testing, obviously nothing in history to worry about. AFTER testing, then there is something that resides somewhere in Memrise that isn’t visually obvious in the course database(s). That has always been the central question. Where do they reside since no one apparently can see them, yet the testing process pulls them up for display as possible responses, (albeit incorrect ones).
Your logic of appending/deleting a letter in each column of a database item did not work in my case. All it seemed to do was create more phantoms with the appended letter on the end of each item. (More than likely I did something wrong when I tried to follow your instructions).
I’m not sure if others (possibly yourself) are claiming that phantom entries are being tested on directly, if so, that is different from what I am seeing, or referring to. In my situation, I am only seeing them as possible choices for another item that is being tested on. Choosing the phantom would obviously be incorrect, but since it doesn’t seem to reside in the database, my issue has always been, why is it even an option as a response for another item. Why didn’t the database row deletion entirely remove it ? Is there a secondary place where deleted entries reside ?
I’m not sure if any of this makes sense to you, or anyone else, but basically, I am back where I was originally. I see things that shouldn’t appear, but can’t delete them. Others do too. I guess only Memrise can shed some light on this issue, or maybe your logic does things that I don’t quite understand. I’m going to just let this issue wallow for a while. I need to focus on other things. I thank you though for your time and effort with this issue. I hope your logic works for others.