Okay, there's a work-around for this bug... For the mushrooms, enter the Evershade instance, go to the meadow where the mushrooms are supposed to be, and log yourself out. When you log back in, there are the mushrooms.
Same works with the Mountain Flowers in Cantermore. This is annoying, but livable.

Did it by utilizing a pair of Climbing Boots to walk around the canyon's rim. Thanks for the pointer, though; I used your method to get back across.

Still happening....