EDIT : FORGET IT, i installed the first patch for V12 ( i didnt noticed there was one lol ) and it's fixed.
Ok so i might have another clue about the trainer not using moves on their pokemon.
Because now it's my turn :
Basically, i use any move on semmingly any of my pokemon, in darchlight wood against wild pokemon and trainer alikes, and i get this error, while my adversary still can attack.
Pretty fucked up bug, i might have to skip the battle by cheating in order to progress at this point...
I'm letting my save here, in case someones needs it. An