Looks like this in UE 4.21:
The UV end of the graph looks like this:

The AutoUV SOP uses these parameters:

The UV islands look like this:

The FBX was exported with these settings:

The FBX works fine in Substance Painter, the resulting maps cover all UV islands, they just don't render properly in UE4. I would like to keep this in FBX rather than as an HDA. The problem is not an outlyer, it occurred with all assets I have tried so far.
