Confused, it seems that when I choose crab L it tells me I chose crab J...
When I chose J it tell me I chose C.. etc

Yes, it is not very clear and you are not the only one, sorry about that :P
In fact, you have to assign a portrait to EVERY crab before clicking on "Check".
"Check" will check all the crabs, not just the one selected.
If I update the game after the jam, I will try to fix that ^^'
Thanks a lot for giving it a try anyway! :D