Just so folks know, you don’t have to wait until you finish the storyline there. Once you unlock that route, you can go to Garchomp. Can easily get to him without flying unlocked as well.
So I already beat the AI Sara for her to teleport herself into the past causing the Time Machine to shut down, but I can’t really get into the cave. I don’t know if I’m missing something or not
The item balls might have been empty for you because you may have x999 of certain types of tera shards, I could be wrong though and it may just be a glitch.