I found that Memrise never remind me to review the difficult words of last course after I finished it.
How to review all my difficult words, no matter, which course that I am learning.
You know, I can review the difficult words of the first few lessons for several times. But about the last few lessons ?
NO. if you changed course, you will be forget them, because, Memrise do not remind you again.
so sad. please help me. thank you !
I study multiple courses simultaneously. Lot’s of the are finished also. I have no problem doing the DW, either by level or bt the whole course. I quite don’t understand your problem, sorry.
Do you delete your course after finishing it? If not just open it and do any DW you have
for example, I learn french level 1. there are 12 lessons in level 1.
that will have some difficult words for me in each lesson and I signed 
and memrise will set up some lessons to review them when I learn new lesson of level 1.
but when I learn level 2, Memrise do not have lesson to review for the difficult words of the last few lessons of level 1, they do not have enough lessons for remember them.
because you changed to level 2.
Are you using a mobile app or web? (I’m guessing app.)
Do you have Pro membership? If you do, you can review difficult words any time you choose. If not, then this feature is not meant for you to use regularly - you just get a taste of it now and then.