Well, if that happens in vanilla worlds, that is sad. I had to delete my character on day 700 to solve the issue and keep my world. That entails reexploring and relearning everything. Hope Klei takes a look at this
I have the same issue and I used to have Gem core and Global Pause in this world. I kinda already thought it was caused by these mods and now I'm even more suspicious
This issue started happening around day 310 in my solo world. Bearger and Deerclops start making their spawning warning at the proper time in the respective season, but after the warning ends no boss appears. At first I thought I just couldn't find the boss, but later I started running the console command to count the amount of prefab (in this case the boss) in the world and it returns zero.
Does anyone know a way to fix this? I would be very grateful, as I don't want to loose this particular world.