I have the same problem with vanilla. But in the dlc, there is a radiation management tool in the sandbox. I tried it out a bit, that's all. next, I switch the mode to vanilla and can not not only download but also start a new game. the error is written
Could not find Klei.AI.Disease: RadiationSickness
at UnityEngine.Debug.LogError (System.Object message) [0x00000] in <b8388ffefd6046f8a7b4080349da72eb>:0
at Debug.LogError (System.Object obj) [0x00000] in <f30d3c85d1f64155aa0dc6c7adb0d1eb>:0
at ResourceSet`1[T].Get (System.String id) [0x00000] in <f30d3c85d1f64155aa0dc6c7adb0d1eb>:0
at SandboxToolParameterMenu.<ConfigureSettings>b__19_2 () [0x00000] in <1c58b1f98f5849baa9083bfd5185b144>:0
at SandboxSettings.<.ctor>b__41_2 (System.String data) [0x00000] in <1c58b1f98f5849baa9083bfd5185b144>:0
at SandboxSettings+Setting`1[T].set_Value (T value) [0x00000] in <1c58b1f98f5849baa9083bfd5185b144>:0
at SandboxSettings.SetStringSetting (System.String prefsKey, System.String value) [0x00000]
I reinstalled the game and all local files are fine