You’ve discovered this already, but you need to regenerate the token if you change the client_id/client_secret.
I hit play on the episode at 18:44:33, and let it run for 10 sec. Hopefully that should be alright log wise. About the peering. It could be possible. I could try to get in contact with Hetzner, so hear if they could try to change it, or maybe use Google DNS (Not sure if an DNS server would help?)
Where is the player located in relation to the server? It looks like Hetzner (Germany?) for the Plex server? Is the player located similar location?
It looks like you are transcoding:
Jan 14, 2019 18:39:39.072 [0x7f51f07fe700] VERBOSE - We want 60 seconds ahead, last returned was 3978.000000 and max is 4041.000000.
Depending where your player is located, that would be the slight lag as things get pushed out to you.
The PS4 is a pretty bad plex client imo and you’ll get a lot of transcodes.