This is a well-known bug. Acer Chromebook R11 CB5-132T, but I understand this is a problem with other if not all Chromebooks. When USB dongle for wireless mouse (I'm using Logitech M187) is inserted, screen auto-rotation does not work when put Chromebook in tent configuration. Have to go to Settings/Displays/Internal Display/Orientation and manually set it to 180 degrees. This is pretty fundamental stuff and has been a known problem for years, how about you guys fix it?