When undocking a laptop from it's dock or disconnecting from a VPN, a blue screen (BSOD) with a Bugcheck 139 error referencing teefer.sys as the cause is seen occasionally.
BSOD with Bugcheck 139 on Teefer.sys
SSL VPN client Citrix Gateway Plug-in
This issue is resolved in Symantec Endpoint Protection 14.2 MP1. Upgrade the Symantec Endpoint Protection client to this version or higher to resolve the issue.