Dell 4032 Stack switch hangs!!!!

Hello,

" switches hangs itself and stop responding, when we go to the site we finds that stack ports leds stops blinking and when we restart the switches every thing comes back normal. [View:/cfs-file/__key/communityserver-discussions-components-files/866/6237.logs.txt:550:0]i have enclosed screen shot of the stack port you can see that leds are off, and also i have attached the logs from the switch  kindly check if you find something suspicious.

we have total 6 sites and similar setup done on each sites and issue i am facing on every site preodically lets say some of the site once in 2 months and other sites once in 4 month"

I have  Cisco 2900 series router connected with dell 4032 switch and created ether channel:-

Cisco port 1 to dell sw 1 port 1 "channel group 1 mode on " on both interfaces (router and switch)

cisco port 2 to dell sw 2 port 1 "channel group 1 mode on" on both interfaces (router and switch)

 what i have done:-

:-there are QSFP module installed into both the switches. form Switch 1 Port 1 connected to Switch two port two, and  switch one port two  connected to switch two port one.  

now Show Switch command shows:-

Management Standby Preconfig Plugged-in Switch Code
SW Status Status Model ID Model ID Status Version
--- ---------- --------- ------------- ------------- ------------- -----------
1 Mgmt Sw N4032 N4032 OK 6.2.6.6
2 Stack Mbr Oper Stby N4032 N4032 OK 6.2.6.6

i have, Dell power Vault MD3820I san Storage with two controller card, each controller have two iscsi ports. and i connected both of them with both the switches. 

like:- controller 0/Port0/Switch1/Port2

         Controller 0/Port1/Switch2/Port2

          Controller 1/Port0/switch1/Port3

          Controller 1/port1/switch2/port3

And,

I have Dell Power Edge R720 Server with dual 10G interface, i have installed Red Hat 7.2. 

and done the Bonding between two 10G interface, Active backup mode.  

10G Port/Switch1/Port4

10G Port/Switch2/Port4

please help to solve this issue. thanks in advance.