I have just edited my database and removed some of the words that were incorrectly entered.
However, although they are no longer in the database they keep showing up in the group of answers to choose from when learning. This is a problem as some of the information has been entered in the correct form but as the English version didn’t change it’s impossible to know which is correct when two same English words appear in the choice boxes.
This has been a problem for years and I have never seen a response to this from Memrise.
Neoncube made a script to fix the problem.
Unfortunately the script doesn’t currently work due to changes to the website.
If your course is a relatively new course and you (and maybe others) haven’t been learning a long time, the easiest solution would be to start from scratch and make a new course with the correct answers.
You could eventually remove the levels (on the incorrect course) but leave the course with a comment to go to your new improve (cloned) course. ie add it to the description and the first level perhaps.