I believe I have a bad development board. I have two robolink sumobot kits where one works and the other doesn't. All states are identical between the two. If I switch the microcontroller to the working development board, it uploads fine. Here's a screenshot of the error from Arduino when uploading to the bad development board:
Moreover, if I take a correctly flashed microcontroller (verified with the working dev board) and move it to the non-working dev board, the robot does not work.