You might come across a situation where the help button (the “?” icon in the quest window) suggests that you need to pick mushrooms located behind a stone wall. However, the path appears to be blocked, making it seem impossible to proceed.

Don’t worry — this is just a small bug with the help button’s hint. There are other mushrooms you can collect instead. Check the accessible area carefully — you’ve most likely missed some mushrooms in a corner of the map. Please refer to the screenshot below: