Rolling upgrade from 172 to 180r-38 failed, unable to determine master node

Steps:-
1) Created a 6node 172 cluster.
2) Load data
3) Swap a 172 node with 180 node.
4) Rebalance

Attaching diags

ERROR:-
Server error during processing: ["web request failed",

{path,"/controller/rebalance"}

,

{type,exit}

,
{what,
{noproc,
{gen_fsm,sync_send_event,
[

{global,ns_orchestrator}

,

{start_rebalance, ['ns_1@10.72.51.127', 'ns_1@10.80.169.159', 'ns_1@10.243.15.240', 'ns_1@10.98.177.74','ns_1@10.2.183.29', 'ns_1@10.211.147.159'], [],[]}

]}}},
{trace,
[

{gen_fsm,sync_send_event,2}

,

{menelaus_web,do_handle_rebalance,3}

,

{menelaus_web,loop,3}

,

{mochiweb_http,headers,5}

,

{proc_lib,init_p_do_apply,3}]}]


ERROR REPORT <0.2671.0> 2011-12-19 20:36:53
===============================================================================

** State machine mb_master terminating
** Last event in was {heartbeat,'ns_1@10.80.169.159',candidate,
[{peers, ['ns_1@10.2.183.29','ns_1@10.243.15.240', 'ns_1@10.72.51.127','ns_1@10.80.169.159', 'ns_1@10.98.177.74']},
{versioning,true}]}
** When State == candidate
** Data == {state,undefined,undefined,
['ns_1@10.2.183.29','ns_1@10.243.15.240',
'ns_1@10.72.51.127','ns_1@10.80.169.159',
'ns_1@10.98.177.74'],
{1324,327011,7604},
['ns_1@10.2.183.29','ns_1@10.243.15.240',
'ns_1@10.72.51.127','ns_1@10.98.177.74'],
compatible}
** Reason for termination =
** {{case_clause,true},
[{mb_master,higher_priority_node,3},
{mb_master,candidate,2},
{gen_fsm,handle_msg,7},
{proc_lib,init_p_do_apply,3}

]}

CRASH REPORT <0.2671.0> 2011-12-19 20:36:53
===============================================================================
Crashing process
initial_call

{mb_master,init,['Argument__1']}

pid <0.2671.0>
registered_name mb_master
error_info
{exit,{{case_clause,true},
[

{mb_master,higher_priority_node,3}

,

{mb_master,candidate,2}

,

{gen_fsm,handle_msg,7}

,

{proc_lib,init_p_do_apply,3}]},
[{gen_fsm,terminate,7},{proc_lib,init_p_do_apply,3}

]}
ancestors [ns_server_sup,ns_server_cluster_sup,<0.51.0>]
messages []
links [<0.118.0>,<0.526.0>,<0.55.0>]
dictionary []
trap_exit true
status running
heap_size 2584
stack_size 24
reductions 725