The trainer slide-in feature doesn't behave correctly in doubles and could use some improvements

[LOuroboros]

Title.

About 2 years ago I brought up how they are a bit glitchy in double battles. This was before the feature branches' development started to happen here instead of in Egg's repository, so I may as well open an issue ticket to get that addressed some day.

Lunos, but written in Japanese 09/05/2019
Oh wait, nevermind, I just killed Meditite first, that's why her trainer's sprite wasn't appearing over it before.
It's still not working that well in doubles.

I tested it on a clean copy of the battle_engine, and effectively, it's still a bit glitchy.

pn_996.mp4

Notice how, for example in the 20 seconds mark, the wrong trainer is being slid-in.
That Youngster doesn't have a Geodude, it's the Hiker that does.
Moreover, after that first slide-in instance happens, the sprite of the Shroomish that remained on the opposing side did not slid out of battle when it was fainted.

From what I can tell after quickly going through the first rival battle against Barry in Pokémon Platinum, the instances where the trainer slide-in messages happen may not be accurate, so that could be improved upon too.
For example, Barry has slide-in messages when his Pokémon first receives damage, and where as the battle_engine has a slide-in message if the opponent's Pokémon is at 25% HP, in Platinum it seems to happen when they're at 50% instead.

pn_993.mp4

[LOuroboros]

Adding to this, in the newer games there's slide-in messages for connecting a Super Effective hit too starting from SwSh.