I added the following line to /etc/crontab on the raspberry pi unit:
*/15 * * * * root /opt/bitfury/start-miner.sh
This restarts the miner software every 15 minutes. Since then the performance is rather stable. Probably some of the chips get stuck and need to be re-initialized once in a while?
Possibly. My hash rate has dropped back to 0 again. Tried stop/start miner but no luck. I'm going to reboot the rpi and see what happens.
EDIT:
There is something screwd up here:
root@bitfury:/opt/bitfury# ./start-miner-console.sh
INIT: 0 chips detected
./start-miner-console.sh: line 1: 6087 Floating point exception/opt/bitfury/chainminer/miner
root@bitfury:/opt/bitfury#