"igazor;c-16543449" wrote:
Festival Lots pretty much by definition have a seasonal lot marker on them. There are really 4 different lots, one for each season. If you add something to let's say the Summer version, it won't be there for the other three. There is also a Construction Mode where what you add only lasts for a sim day or so, and is not meant to be permanent. I'm a bit fuzzy on this myself as I almost never work with these markers.
But there's a detailed tutorial here:
http://www.carls-sims-4-guide.com/forum/index.php?topic=13093.0
Thanks igazor, that now makes total sense as to what's been going on! (well that was a waste of time putting those restaurants in each Festival Ground, I know now when I go to play the next one, it, too, will have changed!)