This isn't hard to understand: the number that underlies the title is relative to the rest of the userbase. As in, your title is determined by what your score is in relation to the person with the highest score for that day. So... if the maximum score goes up further than you go up in the same time period (even if you didn't do anything wrong like get a warning or ban), you can easily lose your title. So, in conclusion, STOP ASKING ABOUT IT. It isn't a bug, it works as intended, and you just have accept that some things you're not going to be able to know the details of.