On the "Edit Event" page, in the "Where" block, there are standard fields for Address, City/Town, State/County, Postcode, Region & Country.
I can fill in all of those OK, except Postcode and Region. Region doesn't really matter, because I don't think I need it anyway, but any entry I make to Postcode or Region disappears when I click the WordPress Update button.
With or without the Postcode, the correct location is being indicated on the map.
Is there any chance that the Postcode field is programmed to only accept a specific format? I'm in Australia where we use four digit postcodes, but I tried a US five digit code with the same result. If it is a restricted format, how can I put the user back in charge of their own postcode entry without interference from code?