I can confirm my team has been experiencing this as well. Several days in game and not a single mushroom farm, dew drop collector, or indeed dew drops on grass stems was respawning. I went from literally one end of the map to the other looking for dew drops on grass and couldn't find a single one.
ADDITIONALLY, and perhaps more troubling: in multiplayer, non-host players were seeing dew-drops on grass which just weren't there at all. This is a host syncing issue similar to the problem experienced with berries: client connections can 'see' dew drops (and berries) that aren't there in the host's game, and which are therefore non-interactable.