nfs storage not responding

Hi,

I am facing this frequent outage issue in storage where NFS clients can’t access exported  folders for 20-30 minutes and then connect back again. 

Configuration:

-          2 windows servers powervault NX3300 (failover cluster)

-          1 chassis 3660i

-          2 extensions 3060.

-          iSCSI connection from chassis 3660 to windows server (1 Gbps)

-          storage servers export nfs storage to linux servers through 10 Gbps ethernet cables.

I am not able to determine a pattern for this outage.

sometime it happens and sometime it is not.

I can find nfs not responding error in the linux client side servers for certain time 

I found some error messages in windows server logs and storage logs as attached. But I am not sure if it is related to outage or not.

Please can you guide me to what might cause this issue?

Thanks.