I've had a response from familysearch support and include some quotes :
"....thank you for your reply and for the details provided. We are passing your feedback to our engineers for their consideration as there is further work to do on the collection."
They go on to state that the have found all the example marriages by
"..conduct[ed] marriage searches by opening 2 tabs in our browser and searching in exact close and partial in the collection for names only. We then apply filters for the event year range and select the event 'residence' in the case of marriage searches to narrow results. We await at present further work to enable filter by registration district."
It looks like the search method for marriages has changed slightly and requires an search on all locations and events first, then filtering on the residence, rather than marriage as before - which was mentioned by aghadowey earlier. Including the the county in the search seems to cause the 'no results' error for many of the recent (19202/30s) births.... as leaving this out returns many of them for me.
I haven't checked other marriages using this method yet.
They also mention they the plan to changing the familysearch website and adding improved search capabilities.
Shane