Heyo - my game is also having issues with this mod. Here's the error generated in game:

Please report this error on the Building Themes workshop page:
ERROR: Comparison threw an exception.
at System.Array.Sort[BuildingItem] (BuildingThemes.GUI.BuildingItem[] array, Int32 length, System.Comparison`1 comparison) [0x00000] in <filename unknown>:0
at System.Collections.Generic.List`1[BuildingThemes.GUI.BuildingItem].Sort (System.Comparison`1 comparison) [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIThemeManager.GetBuildingItemList (BuildingThemes.Theme theme) [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIThemeManager.InitBuildingLists () [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIThemeManager.Start () [0x00000] in <filename unknown>:0

Please report this error on the Building Themes workshop page:
ERROR: Object reference not set to an instance of an object
at BuildingThemes.GUI.BuildingItem.get_level () [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIThemeManager.ThemeValidityError (BuildingThemes.Theme theme) [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIThemeItem.Display (System.Object data, Boolean isRowOdd) [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIFastList.DisplayAt (Single pos) [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIThemeManager.SetupControls () [0x00000] in <filename unknown>:0
at BuildingThemes.GUI.UIThemeManager.Start () [0x00000] in <filename unknown>:0

I just pushed an update:

- Removed various error popups
- Added Art Deco buildings to standard themes
- Added Snowfall buildings to standard themes (again?)
- Removed "Office" from International Theme

Hey, just got this error. It happened when loading a save file and changing the map theme. I don't know if the Environment Changer (+ Improved Theme Selection ) mod is conflicting.
Anyway, heres the error text:

Please report this error on the Building Themes workshop page:
ERROR: Object reference not set to an instance of an object
at BuildingThemes.GUI.UIStyleButtonReplacer.ReplaceStyleButton () [0x00000] in <filename unknown>:0
at BuildingThemes.LoadingExtension.OnLevelLoaded (LoadMode mode) [0x00000] in <filename unknown>:0

Default international buildings not loaded. I have the new version of 81 Tiles. Compatibility issue?

My city has been unplayable for about a month now and it seems to be because of building themes.

I got this error in my output_log file":

(Filename: C:/buildslave/unity/build/artifacts/generated/common/runtime/UnityEngineDebugBindings.gen.cpp Line: 42)

NullReferenceException: Object reference not set to an instance of an object
at ToolBase.OnDisable () [0x00000] in <filename unknown>:0

(Filename: Line: -1)

NullReferenceException
at (wrapper managed-to-native) UnityEngine.Component:get_transform ()
at BuildingThemes.BuildingVariationManager.Reset () [0x00000] in <filename unknown>:0
at BuildingThemes.LoadingExtension.OnReleased () [0x00000] in <filename unknown>:0
at LoadingWrapper.OnLoadingExtensionsReleased () [0x00000] in <filename unknown>:0
UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
UnityEngine.Logger:LogException(Exception, Object)
UnityEngine.Debug:LogException(Exception)
LoadingWrapper:OnLoadingExtensionsReleased()
LoadingWrapper:Release()
LoadingManager:ReleaseRelay()
LoadingManager:OnDestroy()

(Filename: Line: -1)

Just following orders, captain:

Please report this error on the Building Themes workshop page:
ERROR: Exception has been thrown by the target of an invocation.
at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0
at BuildingThemes.Detour.PoliciesPanelDetour.RefreshPanel () [0x00000] in <filename unknown>:0

Please report this error on the Building Themes workshop page:
ERROR: Exception has been thrown by the target of an invocation.
at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0
at BuildingThemes.Detour.PoliciesPanelDetour.RefreshPanel () [0x00000] in <filename unknown>:0

Please report this error on the Building Themes workshop page:
ERROR: Object reference not set to an instance of an object
at BuildingThemes.Redirection.RedirectionHelper.RedirectCalls (System.Reflection.MethodInfo from, System.Reflection.MethodInfo to) [0x00000] in <filename unknown>:0
at BuildingThemes.Redirection.RedirectionUtil.RedirectMethod (System.Type targetType, System.Reflection.MethodInfo detour, Boolean reverse) [0x00000] in <filename unknown>:0
at BuildingThemes.Redirection.RedirectionUtil.RedirectMethod (System.Type targetType, System.Reflection.MethodInfo method, System.Collections.Generic.Dictionary`2 redirects, Boolean reverse) [0x00000] in <filename unknown>:0
at BuildingThemes.Redirection.RedirectionUtil.RedirectReverse (System.Type type, System.Type targetType, System.Collections.Generic.Dictionary`2 redirects, Boolean onCreated) [0x00000] in <filename unknown>:0
at BuildingThemes.Redirection.RedirectionUtil.RedirectType (System.Type type, Boolean onCreated) [0x00000] in <filename unknown>:0
at BuildingThemes.Redirection.Redirector`1[BuildingThemes.Detour.ZoneBlockDetour].Deploy () [0x00000] in <filename unknown>:0
at BuildingThemes.LoadingExtension.OnCreated (ILoading loading) [0x00000] in <filename unknown>:0