Dual mastership is seen on X250-e stack

[Arun1]

All of a sudden, two switches in the stack claimed to be master and caused connectivity issues to the end users. Issue resolved after I rebooted one of the switches which claimed master status.Now I am trying to understand underlying cause. I dont see any suspicious logs apart from the following one.

Slot-1: BACKUP NODE (Slot-2) DOWN

No flaps or errors observed on the stack ports.Stack is running 12.6.5.2 version

[Arun1]

I think no back up is chosen as there are no other master capable switches in the stack . I dont want to enable master capable on any switch before understanding underlying cause. I dont want to be in dual master-ship situation again.

[Arun1]

sh stacking (collected before rebooting slot2)

Stack Topology is a Ring
Active Topology is a Ring
Node MAC Address Slot Stack State Role Flags
------------------ ---- ----------- ------- ---
*00:04:96:**:**:56 1 Active Master CA-
00:04:96:**:**:1d 2 Active Master CA-
00:04:96:**:**:22 3 Active Standby CA-
00:04:96:**:**:5f 4 Active Standby CA-
00:04:96:**:**:5c 5 Active Standby CA-

sh stacking (Collected after the reboot. No backup is chosen. I turned off master-capability on slot2)
Stack Topology is a Ring
Active Topology is a Ring
Node MAC Address Slot Stack State Role Flags
------------------ ---- ----------- ------- ---
*00:04:96:**:**:56 1 Active Master CA-
00:04:96:**:**:1d 2 Active Standby CA-
00:04:96:**:**:22 3 Active Standby CA-
00:04:96:**:**:5f 4 Active Standby CA-
00:04:96:**:**:5c 5 Active Standby CA-

sh stacking detail
Current:
Stacking : Enabled
Role : Master
Priority : Automatic
Slot number : 1
Stack state : Active
Master capable? : Yes
Stacking protocol : Standard
License level restriction :
In active topology? : Yes
Alternate IP address :
Alternate gateway :
Stack Port 1:
State : Operational
Blocked? : No
Control path active? : Yes
Stack Port 2:
State : Operational
Blocked? : Yes
Control path active? : Yes
Configured:
Stacking : Enabled
Master capable? : Yes
Slot number : 1
Stacking protocol : Standard
License level restriction :

Stacking Node 00:04:96:52:b5:1d information:
Current:
Stacking : Enabled
Role : Standby
Priority : Automatic
Slot number : 2
Stack state : Active
Master capable? : No
Stacking protocol : Standard
License level restriction :
In active topology? : Yes
Alternate IP address :
Alternate gateway :
Stack Port 1:
State : Operational
Blocked? : Yes
Control path active? : Yes
Stack Port 2:
State : Operational
Blocked? : No
Control path active? : Yes
Configured:
Stacking : Enabled
Master capable? : No
Slot number : 2
Stacking protocol : Standard
License level restriction :

Stacking Node 00:04:96:52:b5:22 information:
Current:
Stacking : Enabled
Role : Standby
Priority : Automatic
Slot number : 3
Stack state : Active
Master capable? : No
Stacking protocol : Standard
License level restriction :
In active topology? : Yes
Alternate IP address :
Alternate gateway :
Stack Port 1:
State : Operational
Blocked? : No
Control path active? : Yes
Stack Port 2:
State : Operational
Blocked? : No
Control path active? : Yes
Configured:
Stacking : Enabled
Master capable? : No
Slot number : 3
Stacking protocol : Standard
License level restriction :

Stacking Node 00:04:96:52:b5:5f information:
Current:
Stacking : Enabled
Role : Standby
Priority : Automatic
Slot number : 4
Stack state : Active
Master capable? : No
Stacking protocol : Standard
License level restriction :
In active topology? : Yes
Alternate IP address :
Alternate gateway :
Stack Port 1:
State : Operational
Blocked? : No
Control path active? : Yes
Stack Port 2:
State : Operational
Blocked? : No
Control path active? : Yes
Configured:
Stacking : Enabled
Master capable? : No
Slot number : 4
Stacking protocol : Standard
License level restriction :

Stacking Node 00:04:96:52:b5:5c information:
Current:
Stacking : Enabled
Role : Standby
Priority : Automatic
Slot number : 5
Stack state : Active
Master capable? : No
Stacking protocol : Standard
License level restriction :
In active topology? : Yes
Alternate IP address :
Alternate gateway :
Stack Port 1:
State : Operational
Blocked? : No
Control path active? : Yes
Stack Port 2:
State : Operational
Blocked? : No
Control path active? : Yes
Configured:
Stacking : Enabled
Master capable? : No
Slot number : 5
Stacking protocol : Standard
License level restriction :

[Ronald_Dvorak]

Could you please provide a "show stacking" and "show stacking detail"