Mostly posting this because I found no solution online to the problem.
Firstly, the problem: Level syncing in Jade Forest (and presumably completing some quests) will reset your reputation with the Forest Hozen. Continuing through the level sync will not restore this reputation as you are not granted the quest to kill Dook Ookem and end up hitting a wall where you cannot progress anymore due to hostile quest NPCs.
Now, the solution: Fly back and forth over the mailbox at Grookin Hill. Seriously, you get 1000 rep every time. It’s totally crazy and unbelievable, but it worked for me. I’d link some proof but hey, forum trust levels are a thing 