We recently upgraded from 7.15 to 9.9.1 version 

When we re-start our servers (Windows2019) hosting our episerver websites, the CPU usage goes high (100%). When we checked event viewer we saw below exception logged multiple times. 

Exception information:

    Exception type: TargetInvocationException

    Exception message: Exception has been thrown by the target of an invocation.

   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)

   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)

   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)

   at System.Activator.CreateInstance(Type type, Boolean nonPublic)

   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, StackCrawlMark& stackMark)

   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)

   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)

   at System.Web.HttpRuntime.CreateNonPublicInstance(Type type, Object[] args)

   at System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context)

   at System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext)

Initialize action failed for Initialize on class EPiServer.Initialization.Internal.ModelSyncInitialization, EPiServer, Version=9.9.1.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7

   at EPiServer.Framework.Initialization.InitializationEngine.InitializeModules()

   at EPiServer.Framework.Initialization.InitializationEngine.ExecuteTransition(Boolean continueTransitions)

   at EPiServer.Framework.Initialization.InitializationEngine.Initialize()

   at EPiServer.Framework.Initialization.InitializationModule.<>c.<FrameworkInitialization>b__7_0(InitializationEngine e)

   at EPiServer.Framework.Initialization.InitializationModule.EngineExecute(HostType hostType, Action`1 engineAction)

   at EPiServer.Framework.Initialization.InitializationModule.FrameworkInitialization(HostType hostType)

Any ideas what might be causing this error and how we can fix it?