The pattern is the same: Move from one map to another using some portal, then the screen remains black for longer than expected, and then you find yourself in the other map but with the BGM of the map you just moved from. No matter how many times you move to another map, the same BGM of the original map keeps on playing and every time you move to a new map the time it takes is longer than usual. For example, I just exited the Mu Lung Dojo and it suddenly happened. What's weirder this time is that when I logged out the login screen was bugged out. Sorry I couldn't add a screenshot, I clicked on PrintScreen but probably overridden the clipboard history somehow before pasting the screenshot into MS Paint. I have no idea how to reproduce the bug, it happens randomly from time to time. The only solution is to restart the client. Hope I supplied enough information!
Sounds like got lag from bossing or when you play quite a long time. Yeah and the only way is reclient and I think it's normal, not bug. Happen to almost everyone.