Can not add configuration items on mqtt attributes

I have some attributes that are filled by mqtt messages. This is working fine. The problem arises when i want to add a configuration item to the attributes that are listening to the mqtt messages. I can click on “add configuration item” and i can choose an item, however it is not there when i click on “add”. For the other attributes it is working.

This would not have much to do with how the attributes are changed. Are there any logging messages or errors on the logs page?

There are no errors in the log. It might be because the values are constantly updating by the mqtt connection.