rebalance failing in simple-test

The first rebalance test in make simple-test under test running is failing with the following in debug log:

[ns_server:error,2014-01-17T13:38:31.429,n_0@192.168.5.251:<0.6965.0>:misc:inner_wait_shutdown:1555]Expected exit signal from <18610.2412.0> but could not get it in 5 seconds. This is a bug, but process we're waiting for is dead (noproc), so trying to ignore…

[ns_server:debug,2014-01-17T13:38:31.429,n_0@192.168.5.251:<0.6965.0>:misc:inner_wait_shutdown:1556]Here's messages:

{messages,[]}

[ns_server:error,2014-01-17T13:38:31.429,n_0@192.168.5.251:<0.6965.0>:misc:sync_shutdown_many_i_am_trapping_exits:1537]Shutdown of the following failed: [

{<18610.2412.0>,noproc}

]
[ns_server:error,2014-01-17T13:38:31.431,n_0@192.168.5.251:<0.6965.0>:misc:try_with_maybe_ignorant_after:1573]Eating exception from ignorant after-block:
{error,{badmatch,{ok,

{mc_header,137,1,0,0,0,16,0}

,

{mc_entry,<<>>,<<>>,0,0,0,<<"Engine not found">>,0}

}},
[{ns_replicas_builder_utils,kill_a_bunch_of_tap_names,3,
[

{file,"src/ns_replicas_builder_utils.erl"}

,

{line,52}

]},
{misc,try_with_maybe_ignorant_after,2,
[

{file,"src/misc.erl"}

,

{line,1571}

]},
{gen_server,terminate,6,[

{file,"gen_server.erl"}

,

{line,722}

]},
{proc_lib,init_p_do_apply,3,[

{file,"proc_lib.erl"}

,

{line,227}

]}]}
[error_logger:error,2014-01-17T13:38:31.432,n_0@192.168.5.251:error_logger<0.6.0>:ale_error_logger_handler:log_msg:76]** Generic server <0.6965.0> terminating

collected cluster_run logs attached