We have workflow running on a document library in SP 2013.
Most of the time workflow executes fine. However, once in a while we get an error in one particular action which calls the web service.
The error is:
Failed to invoke web service. Error returned from server: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.
The action is configure as shown below:
The only strange part is the error is completely random. It does not happend for any specific user or scenario.