Next to your mini map is a row of buttons. One of them is a question mark. Click it, it'll bring up a menu. One of the menu options will be "report a bug" or something like that. Click it, click the appropriate bug category, and write as much detailed info as you can.
After it's reported, you'll get a ticket ID #, which you can post in this thread so any devs/QA that do happen to read will know right where to look.