vRA DEM Error : Error : Workflow vSphere SnapshotInventory failed with the following exception

HIi All,

We are having vRA 7.4 version , nowadays we are frequently getting below error in vRA LOG tab against DEM server

Error: Workflow vSphere SnapshotInventory failed with the following exception :

          The Underlying connection was closed: An  unexpected error occuredm on a receive.Inner Exception: THe Underlying connection was closed

NOTE :

1. We are having CA Signed certificate for all vRA infra
2. DOT Net framework 4.5 is installed
3. Windows 2012 OS is in use for vRA infra serevrs.
4. vRA vesrion is 7.4

Please suggest