So… My problem is simple:
Server crashes with sponge: Duplicate Id
I tried deleting many, many, many mods, however, without these mods, modpack isn’t modpack…
So… It happens just with sponge installed. With forge only, it’s okay.
I don’t know what is causing this, because it ONLY prints sponge-related errors and does not leave any traceback to any mod causing this… It’s really, really weird.
Thanks for feedback!