Which Raspberry Pi firmware did you use ?
This may occurs before this one,
https://en.bitcoin.it/wiki/Avalon6#20160125.
We always use the latest Raspberry Pi firmware with the latest Avalon Miner 6.0 MM firmware.
Anyway We still work hard to keep backward.

New MM firmware released for AvalonMiner 6.0, Hardware model: MM-60, Version: 601605-256e0f00
Firmware Details:
http://downloads.canaan-creative.com/software/avalon6/mm/2016-05-11/
ChangeLog:
* Check api fifo overflow
* Add CODE_HOTBEFORE for hot notify
* Add a new package AVA4_P_SET_FREQ
* Support device hardware error
* Fix duplicate share
* Move stratum file to a lib
* Update temp check
Communicate:
http://lists.canaan-creative.com/cgi-bin/mailman/listinfo
IRC: #avalon @freenode.net
Documents:
https://en.bitcoin.it/wiki/Avalon
time to try some new firmware
Tested it and I can't get my daisy chain to work ... I see all 4 in the UI but only one is hashing
EDIT: did a rollback to the previous version. working now.