Several customers reported problems with ArcGIS Server / UT Server. Thereby the ArcSOC.exe processes were not terminated when terminating map services or single instances of map services. These "zombie" processes continued to allocate memory and this ultimately led to memory bottlenecks on affected systems up to a system failure.
We were able to trace the cause of this behavior back to a faulty display driver in a virtualized environment based on VMware. All customers were using VMware for virtualization and the problems occurred after updating the VMware tools to version 11.2.5. The installation of "VMware, Inc. By installing "VMware, Inc. - Display - 18.104.22.168" (https://www.catalog.update.microsoft.com/Search.aspx?q=vmware) the problems could be solved in the cases known to us.
Not only ArcSOC processes of the ArcGIS Server are affected by the problem. The misbehavior could also be traced for processes of the WMPS. During our research we came across comparable problems in the AutoCAD environment. We therefore assume that this problem is of a general nature and can affect various processes and applications. We therefore recommend that customers who use VM Ware for virtualization check their environments (not only in the environment of our products) for similar behavior and install the above-mentioned display driver if necessary.
In the meantime, there is also an article from VMWare that describes the problem.