Trying to install a stack onto a pawn caused a straight up crash, checked logs and found:

Error while determining if Dr. Barbara should have Need VAEI_Sanity: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object
[Ref 4EAEE095]
at Verse.Find.get_FactionManager () [0x00005] in <630e2863bc9a4a3493f2eff01e3a9556>:0
at RimWorld.Faction.get_OfHoraxCult () [0x00000] in <630e2863bc9a4a3493f2eff01e3a9556>:0
at VAEInsanity.Need_Sanity.SetInitialLevel () [0x0000b] in <119f25212aea441a9a34f4af559e462e>:0
at <0x1efb2912300 + 0x00036> <unknown method>
at <0x1efb2919d00 + 0x000d2> <unknown method>
at (wrapper managed-to-native) System.Reflection.MonoCMethod.InternalInvoke(System.Reflection.MonoCMethod,object,object[],System.Exception&)
at System.Reflection.MonoCMethod.InternalInvoke (System.Object obj, System.Object[] parameters) [0x00002] in <eae584ce26bc40229c1b1aa476bfa589>:0
--- End of inner exception stack trace ---
[Ref 3D1AD7DD]
at System.Reflection.MonoCMethod.InternalInvoke (System.Object obj, System.Object[] parameters) [0x00014] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.Reflection.MonoCMethod.DoInvoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x0007a] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.Reflection.MonoCMethod.Invoke (System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.RuntimeType.CreateInstanceImpl (System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, System.Object[] args, System.Globalization.CultureInfo culture, System.Object[] activationAttributes, System.Threading.StackCrawlMark& stackMark) [0x00213] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.Activator.CreateInstance (System.Type type, System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, System.Object[] args, System.Globalization.CultureInfo culture, System.Object[] activationAttributes) [0x00095] in <eae584ce26bc40229c1b1aa476bfa589>:0
at System.Activator.CreateInstance (System.Type type, System.Object[] args) [0x00000] in <eae584ce26bc40229c1b1aa476bfa589>:0
at RimWorld.Pawn_NeedsTracker.AddNeed (RimWorld.NeedDef nd) [0x00040] in <630e2863bc9a4a3493f2eff01e3a9556>:0
- PREFIX VREAndroidsMod: Boolean VREAndroids.Pawn_NeedsTracker_AddNeed_Patch:Prefix(Pawn ___pawn, NeedDef nd)
- PREFIX VPEPuppeteerMod: Boolean VPEPuppeteer.Pawn_NeedsTracker_AddNeed_Patch:Prefix(Pawn ___pawn, NeedDef nd)
at RimWorld.Pawn_NeedsTracker.AddOrRemoveNeedsAsAppropriate () [0x00033] in <630e2863bc9a4a3493f2eff01e3a9556>:0
- PREFIX OskarPotocki.VFECore: Void VFECore.AddOrRemoveNeedsAsAppropriate_Patch:Prefix()
- POSTFIX OskarPotocki.VFECore: Void VFECore.AddOrRemoveNeedsAsAppropriate_Patch:Postfix()

Uninstalled VAE - Insanity, and it worked fine after that.

Unsure if this is a AC2 issue or VAE - Insanity one