The same issue is happening to us. Vsphere 6.5, virtual hardware verssion 13 with windows 2016 and windows 2012 is not working well. In one w2012 R2 we have a file server and intermitent disconnections occurred... a big disaster as we had to downgrade the virtual hardware to all 2012 an 2016 vms.
After downgrade to virtual hardware 10 (w2012) and virtual hardware 11 (w2016) the issue disappears and all comes to life as usual...