Missing Collection parts in SBIM Collection

Some elements are included in the Collection, but they are missing from the Infra Browser. If I refresh the Axis, the elements that are missing from the Infra Browser disappear from the model as well. What could be causing this problem?
When I isolate the Collection in the Infra Browser, all of its elements are shown. However, when I isolate the individual rows one by one, the missing elements cannot be isolated.