If this is only happening on Muppet I would suggest going into the Muppet Blueprint and make sure each of the Interface Functions are all setup. Sometimes they can get unhooked when migrating. For the behavior you are seeing I would check the Interface Function GetContainerInventory first to make sure it is returning a reference of Muppets InventoryComponent.
If you are still having issues drop me a message at support@vanguardinteractive.com