Personal feeds presumably can save any item from content feeds generated in Feedigy. However, some public and imported feeds can be invalid, have bugs and errors in the source code, or miss important parameters. Unfortunately, we don't have control over such feeds and sometimes can't process items from such feeds.
In case we are not able to add an item to your personal feed, you will see this error message:

Another way around - add this item manually. Create a new item in your personal feed and copy/paste content from the needed item.