All information here: Rebirth-of-the-Night/Rebirth-Of-The-Night#710

TLDR: When on a server with a player, any chapters that unlock after obtaining an achievement require a relog to the server in order for that chapter to unlock.

On singleplayer, the chapter is unlocked immediately after obtaining the achievement.

ugh

I cannot reproduce this with just Patchouli, which is horribly annoying. I guess I could prepare some build with extra spammy logging for testing purposes for you?

You tested it on a server I presume? But yeah i can do some testing with a debug build

A local server, but yeah. I'll look into that tomorrow after work.

This issue is stale because it has been open for a while with no activity. Please bump if this is still an issue, or this ticket will be closed soon.

still an issue to my knowledge, what was the result of said testing or whatever

The result of testing was that I couldn't reproduce it on a Patchouli-only multiplayer server (so it must be a mod interaction...) and then I forgot to test with other mods, and had no motivation to continue once I remembered.

I'm sorry, I just don't have that too much free time and don't have the motivation to bisect a big modpack to see what might cause the issue.