Multiple CAPC Reporting Groups have been populated and reporting for multiple months and have lost item inventory and rule functionality.
If this behavior exhibits itself, it is likely that the items in question have been Excluded or Removed. Either process adds an entry in the MySql deleted_item_members table that references the itemid of the item and the parentid of the group to link them together.
When running a group rule, the rule is processed but before the contents are saved, a check happens against the deleted_item_members table. If any entries exist here, they will not make it through the running of the rule.