Same issue in here. Using v 4.3.1 on Windows. It's happend only when I'm currently on "Show structure" page and from there I do click on "Alter table". Actually when I'm on "Show structure" page all of the links pointing to the other actions are with table name in lowercase. So the only way to alter my table without changing the letter's case is to go at the page "Select data" at first and from there is't "safe" to go at "Alter table"