Load an authoritative list with > 200 taxa into Spatial (example: "Birds of Western Australia", 537 taxa) - dots will eventually show on map, "Loading" will appear perpetually until you click Cancel - info button shows 505 species so it looks like all species were successfully added (possibly there were 0 occurrences for some).
If you add the exact same list again immediately after, this time the "Loading" box will go away once dots are appearing on the map. This is consistent and repeatable by opening a new tab/session of Spatial and doing the same thing, suggesting the perpetual "Loading" screen is a byproduct of having to load/cache the contents of a list or its records only the first time in a session.
Authoritative lists with < 200 taxa seem inconsistently affected - I've not seen it happen with a list of 14 species, it happened once with one a little below 200 (and then would load first time every time in new tabs).