What is an "error -12" error?

A Kaseya agent maintains a persistent TCP/IP or domain connection to the Kaseya Server it is pointing to. Additionally, the agent is also set to continually check in every 30 seconds by default in addition to the persistent connection it works to maintain with the Kaseya Server. 

"Error -12" errors and these types of messages can occur all the time between Kaseya Server agents and the Kaseya Server they point to. There are legitimate times to look into these errors and many other times, error -12 reports are recorded due to minor connectivity and communication drops within the persistant TCP/IP or domain agent connection. Additionally, agents are set to check in every 30 seconds by default.

With that stated, legitimate error -12 and messages noted above-type issues do occur. This is especially evident by repeated entries in the kserver.log file and agent log files, usually when an agent is not able to complete a task it completed perviously (ie.: audit script execution, remote control, etc...) anymore. Some firewalls or firewall servers will drop this persistent connection if the connection is idle too long from one end, be it at the Kserver or Agent end. In these constant/repeated -12 scenarios, the network is most likely needing resources elsewhere and the communications will be dropped from the agents connections to use those network resources for whatever else it is on your network that is in need of it. Verify if there is any firewall-related activity occurring with the agent machine reporting the error -12/error messages when an agent is not able to complete a task it completed perviously. Verify the persistent connection timeout settings on both the Agent machines network hardware setup as well as the VSA machine network hardware setup too. Increase this to verify if behavior changes from here. Consult with your network vendor should these errors continue to appear.  Also consider A/V / File Security software settings.