When I convert items from non-stackable to stackable, the items don't get consolidated in the player's inventory. See player 9A7AE96546CEE8C4 in title 6263, and search for "Teddy Bomb" - there's multiple entries. All the entries link to the current, stackable, object.
Correct - instances of items are distinct from the catalog. Think of the catalog as the definition for how items are to be created. When the items are instanced, they are created from that template. So if the item is not stackable when it is instanced, changing the catalog will not change the already-existing items. While I realize it seems unlikely that it would actually break an existing title, we cannot make potentially breaking changes to the service for non-critical issues.
The way to resolve this for your users is by using Cloud Script to replace the items in question, granting the ItemId in its new state and revoking the old instances. Since you can only revoke one item at a time, and you need to be careful not to have the scripts run too long or make too many API calls, this is going to need a client update, as well. Ideally, I would do it this way: When the client gets the inventory for the first time in a session, check it for this issue. If it has any items in this state, have it make a series of calls to Cloud Script over time to update the inventory to replace the item.
Here's the problem with that plan: I can't tell whether a version in the inventory is Stackable or not. That information doesn't appear in the inventory result.
Further question: If a stackable catalog object's info changes (for instance, an item class, expiry time, bundle contents, custom data), and then a player is granted another one, their version will still have the original attributes?
Yes and no. Because stackable items stack onto their base, the base is what defines its static properties, so class, tags, image URL, description, and display name would all remain the same. However:
If you need to change the static elements on a stackable, the current recommendation would be to move to a new ItemId (and again, then use Cloud Script to move the old items over). I'm adding a backlog item as well for an "overwrite base" option for catalog items, though I will caution that it will likely be some time before that bubbles up in the priority stack.
