Kanban plugin - error on moving tile on a kanban board based on activity status

It is very strange you don't get an error.
Result of request in browser concole is ERROR 500 : it means server error, so an error should be logger, at least in apache error log.

Reply posted (also nedd DB backup)

OK, I installed an instance from your data.
I connected as admin and accessed to Kanban.

I first accessed "Kanban Activité", managing activities, where I could move items from "En cours" to "Terminé"
I could move some activities (for instance #7) from "Backlog" to "En cours", but not all as I got a blocking message "le champ 'date de fin validée' est obligatoire":

Then I accessed "Kanban", managing Tickets.
There, I could not move any item : when you get a ticket and move it over another column, header is always red showing that move is impossible. Header is green only when Ticket is over his own column.
This means that the Workflow forbids the move : You cannot move the items from their current status to the first status of any column.

If it is the behavior you get, this is normal, the definition of your Kanban doew not fit the definition of the workflow.
If your behavior is different, please explain it step by step, using ids :
- wich user is connection (id of user)
- which kanban is used
- which item (id) is moved, from where to where...
Thanks