Forge version: 14.23.1.2555
Twilight Forest version: 274 - 296
Link to crash log: https://pastebin.com/Ew5X7GVr

OTG multiverse functionality is broken in builds 274 - 296, where vanilla dimensions and dimensions added by other mods (e.g. Aether Legacy) are unaffected. Entering secondary dimensions created through OTG results in a crash.

Posting this even though these are experimental builds because it isn't the sort of thing you would test before a release version.

Might be related to #334, since they share a similar crash report

Looks like #334 (comment).

https://github.com/PG85/OpenTerrainGenerator/blob/1.12-OTG%2B/platforms/forge/src/main/java/com/pg85/otg/forge/OTGWorldServerMulti.java#L66-L87

They must call the super method