In my side, I have deleted the subfolder:
C:\Users"your user"\AppData\Roaming\Steinberg\Groove Agent_64
I reload Cubase, then Groove Agent 5 recreate all xml files and that’s ok now!
I can see the correct content list of intruments (kick, crash, hihat etc.)
… some times further…
Hem… yes it was working on a new project but ! With my previous one the same result.
So I tryed to update the default.xml file to find the issue but the first time ok but then… the same!
Finally I found a workaround when I select only (not all) but only one instruments sets!!