Learning type filter in the Learning Catalog not showing all available items

Summary:

When using the Learning Type filter in the Learning Catalogue, the number of communities, courses and specializations are not accurately reflected in the search.
E.g. Course is showing 46 when there are actually over 1000. Specialization is showing 2 when there is actually over 100.

Content (please ensure you mask any confidential information):

We are using custom roles however these have been checked and tested against the oracle delivered roles and do not change the outcome.

We use access groups to allow learners to view the learning items and so the default access on each individual course is not used.

Is anyone aware of anything else which may be preventing the correct number of items appearing in the search?