python - Riak returning locked status when storing key -

i have 5 node riak cluster , doing basic application testing python riakclient using pbc. code looks this:

b = riakclient.bucket('test') item = b.get('key1') item.data = 'testdata' item.store() 

i getting {error,locked} riakerror back. once starts happen lot of errors between cluster nodes this:

handoff receiver partition 1134123.... exited abnormally ... {error,locked} 

any ideas might or how resolve? riak 2.0.2, thinking updating hoping not have yet.

update: problem manifested after docker (did mention that?) container using restarted. after restart riak process came not in functioning state despite being marked healthy in cluster. 'sv restart riak' got cluster working. still wondering means, not seem documented although seem mean node in read-only state.

this problem in shutdown scripts, node coming in unclean state. restart fixed issue.