Why did Defog fail in this battle?

Question

turn 6
Edit: In case you didn't know, the evasion clause bans double team and minimize and has no effect in-battle.

Comments

I Believe it failed because there was nothing to clear. If you notice, it did lower your evasion, so it did something, but just couldn't clear anything from the field.

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Bulbapedia says defog doesn't fail even if there's nothing to clear. Are you sure about this?

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Looks like it didn't clear anything on its side.

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lol. You guys...

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Why was this flagged?

Answer 1

This was a Showdown! bug and has been fixed.
source

Answer 2

Okay, it took me some time, but my cousin made a video showing that Defog will not fail then used in a battle. Also, since you were on showdown, the most likely reason is that there was no fog to clear.
This is the video. Sorry that it cuts off late and has some glare.