What do I set GUID to in Feeds Import? I was told I should use GUID and tick Unique setting for best method of filtering out duplicate content each time cron runs. But what do I set GUID to? My XML sources has like only ,  etc.

Now I am using Title as unique for duplicates. But I get lots of random issues, Feeds Import doesn't import all feeds after each cron, or even better, it gets stuck e.g. 'Importing 48%' and etc.

I got 4 feed imports that parse XML from external site, all from same site (also Drupal). Also I use custom module to trigger them when running cron, because by default Feed Import doesn't even react to hourly cron.

So trying various solutions, maybe this GUID thing will solve this.

I also use XPath XML parser.
You can use a the node or article URL as it's Unique and a lot of feeds use it with no issues at all