Which is seriously causing problem. When we created a support case, CO asked us to fix the iSCSI sessions. We fixed iSCSI sessions from some of the hosts (Windows 2016) servers but still receiving these messages from all of the hosts. Where to start looking for more information ?
Going through Support is the best way forward. Have you provided AutoSupport bundles to Support? They can look through them and see if we see any anomalies on the array side. Have you looked through your Windows server logs to see if anything is wrong there? What about your network configurations and logs? The problem could be with any of these components and essentially you will have to troubleshoot all the pieces involved. A good tool to use would be wireshark if you are familiar with it.