Troubleshooting destination rule firing without user intervention

First, I think this is the proper forum to post your question to. The moderator would let you know if not ;-) 

Back to your technical question...It depends.

This may be 'by design'. If there are escalations that fire (i.e. after 3 days) and causes the process to move on.  Or the process has been re-routed by an admin using a 'Go To' (expires all activities and goes to a specific Activity), or a task has 'Expired' which can also have some processing done beyond the interaction from a user (server event rather than a client event).

K2.net has been around for quite a while, and given no 'phantom' processing has been reported before occured before (barring the items I list above), I am apt to think it is explicitly "by design", though maybe not remembered (developer left and didn't share the logic) or documented (not in technical specifications of project) etc.

HTH.

Thanks for your suggestions.  I have ruled out escalations, someone performing a Go To, and expired tasks.  I'm in the process now of checking system logs and looking at workflow variables.  As this situation happens once a month, I think I should add diagnostic debug statements and then wait for the next production build to deploy it.