VM in Hyper V is hanged

Hello Expert,

I have four VM (say VM1, VM2, VM3, VM4) in microsoft HyperV platform, but some time I can not ping or RDP on VM4, until I restart the VM4, but other three VM are working fine and even there is no problem in network setting, I face this problem twice in a week, then I restart VM4, then it works. Please suggest.

Swaprakash..