It's unlikely to be TM:PE causing that problem as TM:PE does not run in the editors.

You can find list of known editor breaking mods using this tool: https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2034713132
^ That will list mods known to break editor.

Hey, I think I found what might be causing your map editor to break - Network Extensions 2!

I was just looking at a log file from one of the support channels and it had this in it:

TFW: System.MissingMethodException: Method not found: 'ToolsModifierControl.get_isMapEditor'.
at (wrapper managed-to-native) System.RuntimeMethodHandle:GetFunctionPointer (intptr)
at System.RuntimeMethodHandle.GetFunctionPointer () [0x00000] in <filename unknown>:0
at Transit.Framework.Redirection.RedirectionHelper.RedirectCalls (System.Reflection.MethodInfo from, System.Reflection.MethodInfo to) [0x00000] in <filename unknown>:0
at Transit.Framework.Redirection.Redirector+MethodRedirection..ctor (System.Reflection.MethodInfo originalMethod, System.Reflection.MethodInfo newMethod, System.Reflection.Assembly redirectionSource) [0x00000] in <filename unknown>:0
at Transit.Framework.Redirection.MethodInfoExtensions.RedirectTo (System.Reflection.MethodInfo originalMethod, System.Reflection.MethodInfo newMethod, System.Reflection.Assembly redirectionSource) [0x00000] in <filename unknown>:0
at Transit.Framework.Redirection.Redirector.PerformRedirections (UInt64 bitMask) [0x00000] in <filename unknown>:0
at Transit.Framework.Hooks.HooksInstaller.Install () [0x00000] in <filename unknown>:0
at Transit.Framework.Prerequisites.ModPrerequisites.DoInstallation () [0x00000] in <filename unknown>:0