sync_persistence returns #134 error when invoked while client is loading data

(3654067612, 0, [

{'cas': 10526, 'vbucket': 5, 'event': 'persisted', 'key': 'test0'}

])
(2665120453, 0, [

{'cas': 10527, 'vbucket': 2, 'event': 'persisted', 'key': 'test1'}

])
(3519634689, 0, [

{'cas': 10528, 'vbucket': 11, 'event': 'persisted', 'key': 'test2'}

])
(2076783204, 0, [

{'cas': 10529, 'vbucket': 12, 'event': 'persisted', 'key': 'test3'}

])
(239598749, 0, [

{'cas': 10530, 'vbucket': 8, 'event': 'persisted', 'key': 'test4'}

])
(3500687529, 0, [

{'cas': 10531, 'vbucket': 15, 'event': 'persisted', 'key': 'test5'}

])
(1657799731, 0, [

{'cas': 10532, 'vbucket': 6, 'event': 'persisted', 'key': 'test6'}

])
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "synctest.py", line 18, in dotest
res = mc.sync_persistence([

{"key": k, "vbucket": mc.vbucketid}

])
File "/Users/daleharvey/src/membase/2.0/testrunner/lib/mc_bin_client.py", line 335, in sync_persistence
(opaque, cas, data) = self._doCmd(memcacheConstants.CMD_SYNC, "", payload)
File "/Users/daleharvey/src/membase/2.0/testrunner/lib/mc_bin_client.py", line 103, in _doCmd
return self._handleSingleResponse(opaque)
File "/Users/daleharvey/src/membase/2.0/testrunner/lib/mc_bin_client.py", line 96, in _handleSingleResponse
cmd, opaque, cas, keylen, extralen, data = self._handleKeyedResponse(myopaque)
File "/Users/daleharvey/src/membase/2.0/testrunner/lib/mc_bin_client.py", line 92, in _handleKeyedResponse
raise MemcachedError(errcode, rv)
mc_bin_client.MemcachedError: Memcached error #134