Problem with the order in lists that I have created

Hello to all, this is my first post here although I'm a IMDb member from Febreary 2004.

I use to consult, collaborate and create lists on IMDb and never I had any problem.

But from 2 or 3 months ago I tried to add new films to my lists and then I wanted to alphabetically re-order items according to my criteria and surprisenly this happens to me. I thought it were a temporal problem but persists.

I add a new film to my list without problem but when I'm going to put it on its place the list show me some items in the same position

and change the position that I choose for other random position. It's horrible to try to manage this. Every time that I save the list the film is moved to other place or other elements change their position. For example I tried to move 'La carta esférica' after 'La carta' but it was moved after 'Kika' as you can see: