Remove unneeded state.
Synchronise blinking, for real this time.

These arduino's don't exactly have a very stable clock source, but by syncing
every master heartbeat, we can at least pretend they're all the same.

Somehow, the synchronised blinking is kind of creepy...
After discarding duplicate, immediately shift next packet from fifo.
Blink slower.

This way, small sync errors are less noticeable.