Normally I learn 5 words at a time when studying the courses I have made myself. However, this particular session I did some errors and didn’t complete all five words i.e. I did a lot of misstakes so Memrise didn’t consider that I learnt some of the words. Ever since that session Memrise only gives my four words a session when learning new words, and just a few minutes ago, after doing a simple error when learning a new word, it changed to three new words per session. Strange thing is that this only applies to one of the levels in my course, when studying the other levels the system is back to teaching me five words a session.
Memrise doesn’t mix levels when setting up learning sessions. If you only have three words left to learn in a level, then you will have a three-word learning session. Just power through the left-over words.
If you think it might be worth it, you could try restarting just that level. This is the first time that I think I’ve heard of something like this, though, so I don’t know if that would help or not.