The Trials: Oasis Guardian defeated, but no next trial

In The Trials, I’ve found a case where there are no enemies, I’ve killed the oasis guardian, but no mushrooms appear.

Is there a reason for such a phenomenon?

Have you tried walking your character up to the next oasis? I’m wondering if it is a limitation on your current glasses which prevent you from seeing them …

I am wearing Twilight Glasses, and besides, they appear on the map, if not in my character’s line of sight.

Hint: Moving to the next Oasis unlocks a new battle (and mushrooms)…

That’s not how it works. Once you defeat the first oasis guardian, the next set of mushrooms automatically appears.