I know this thread is old, but i have the same issue. My environment consist of 2 windows server 2012 r2 and have HyperV fail-over cluster. i have about 30 VMs and have iscsi connection to a Dell SAN. we use veeam to backup. it happen to different vm, on different host. and it is not every night. but only happen at night. i have done everything, patches, updates, turn off VMQ. Each host have about 384GB of RAM. any solutions?