The service stops quite often for us. We don't export XML files, but we do use SMTP notifications. I'll get a call from someone saying that they aren't getting emails from the system and I re-start the service. I wrote a Windows task to automatically re-start the service daily which helped. But sometimes it just doesn't re-start, then I have to do it manually.
Instability and questionable functionality is one of the major reasons we do not utilize ePDM for our advanced functionality. (Read Workflow, alerts, and Checkcycle for drawing releases.). There are many puzzle pieces there but gaps such as this made it obvious we should go a different direction. We landed on a custom system and have not looked back.
So to sum up, yes we experienced this and more. When you have worked with enough PDM / PLM systems it becomes obvious what one is built for and further obvious when the gaps are not going to be filled for the system to become something it is not. Sometimes one must let a cow be a cow and not ask it to be a goat. ePDM is great for what we pay for and what it is built at its core to do.
We've had this problem in the past. It usually occured after a reboot of the DB server. We solved it by setting the Enterprise PDM database server service to 'delayed start'.