There's already some 'hacks' to cope with API giving an empty response (at beginning of getting the list) but much harder to know if this was a failed response or one of these cases. Really the API should be returning a { groups: [], nextPageToken: null } for this empty page not just {}
Believe we now have 6201 groups so the pipeline should at least succeed next run, even if this issue hasn't been resolved.
Trying to avoid hideous hack that goes, "we failed with an empty response multiple times, yet we had already do some groups, so try again with a different page size and see if we get them correctly this time"...
Spoke to soon, of course there are more than 6200 group in Lookup but until the sync can get all 6200 from Google it won't create the new ones... I'll fiddle the number in Google to get this sync to catch up.