According to the spec, items is a set, while orderedItems is an (ordered) list. This is due to the JSON-LD serialization of AS2: JSON-LD defaults to unordered sets. When using list, some clients may not be able to show the Activities in the right order. To fix this, the OrderedCollectionPages should contain orderedItems instead of items.

• I searched or browsed the repo’s other issues to ensure this is not a duplicate.
• This bug happens on a tagged release and not on master (If you're a user, don't worry about this).