I see that a couple of other people have had this problem, but there don’t really seem to be good answers posted. I apparently uploaded a sketch (~25KB of flash, 1800B of RAM) that somehow made it impossible to upload new sketches. The sketch I uploaded actually seems to be operating properly (and I can boot it into flashlight mode), but nothing I do seems to let it program a new sketch. I’ve tried resetting it and programming it within the 6 second window (probably 30 attempts before I gave up). Switching USB ports, changing the order of unplugging/plugging/powering on/off/etc. has no impact. When I hit upload it causes the arduboy to reset, but then it just boots into the application again.
I am using Arduino IDE 1.8.0 on Ubuntu 16.04. I had previously experienced this problem, and while trying to reset it to program it, my arduboy became completely unresponsive and required replacement, so I am nervous about trying to reset it too many times. Could someone at least explain what exactly is going on when it’s in this state? I actually work with embedded electronics for a living, and I’ve never used a platform this flaky before.