Doesn't change anything.... it is an interger type.
I will try by making a new database and see what will happen.
Some strange problem. I will let you know if a different DB will change anything. Although that should not be the answer of this problem.
I made a new MYSQL database and added the tags to that one. It worked for like 3 minutes and then they stopped again.
Based on this I think it's not something with the DB.
I'm completely out of ideas. Time to open a support ticket.