There has been a number of cases opened with CA for issues with performance on virtual machines running VMWare's VMotion product. The VMotion product is designed to have little to no impact to the virtual machines. Most cases are resolved by disabling the VMotion tool. API Gateway's performance and stability improve.
The exact reasons for this is unknown to CA but it could be related to the allocated resources to the virtual machines as well as dedicated vs. shared resources.
If you are running into unexplained API Gateway server performance or crash issues and you are running VMotion, please disable the tool to eliminate the variable. If stability improves, you may want to reach out to WMware Support for suggestions. They may have suggestions on how to configure the ESX server to minimize or eliminate impact to the virtual machines.