It works as intended now as there was a fix a couple days ago regarding the turn order. It was bugged before that fix a couple days ago.
Some effects like leftovers, perish song turn etc. dont get triggered on switch-in anymore.
If you still think there is an issue it would be nice if you can send screenshots of the battle-log to understand your issue better.
Its actually not a bug as it will only try to evolve upon actually reaching the maximum amount of happiness during daytime. To reach the max happiness again make your pokemon faint in a wild battle and then gain some happiness again during daytime.
Also happiness evolutions dont require a level-up.
Did you do that as suggested? It is not enough to beat the boss in the underwater area, you have to go to another room and interact with the rock in there.
Hey, go back to the forest area to make sure you beat the forest boss. To access the boss room again interact with the treestump with mushrooms on it.
To enter the underwater area make sure to wear the Greninja outfit and interact with the rock in the room back in the underwater cave after you beat the boss in there if you havent already.
Go back to the mountain area maze and talk to the Golem again after defeating the Charizard-X boss there if you havent already.
Its a special form you can encounter only in PRO itself. There are special sprites for different events like easter, christmas, halloween, summer etc. for certain pokemon which you can encounter rarely.
You can see all different sprites which are available when their event is going on here: https://wiki.pokemonrevolution.net/index.php?title=Pokémon_Counterparts
It will only try to evolve upon actually reaching the maximum amount of happiness during daytime. To reach the max happiness again make your Budew faint in a wild battle and then gain some happiness again during daytime.
Also happiness evolutions dont require a level-up.