I've just tried to upgrade (via NuGet) from v8.5.3 to v8.6.0. The NuGet process worked (AFAICT) and the project compiled. When I tried to start my site I was asked to login to the back office. The URL indicated I needed to authorize the upgrade. Despite logging in multiple times and always getting the green tick (for a successful login) I kept being asked to login again.

I've checked the log and found this exception:

{"@t":"2020-04-03T13:29:08.8528880Z","@mt":"Unhandled controller exception occurred for request '{RequestUrl}'","@l":"Error","@x":"System.NullReferenceException: Object reference not set to an instance of an object.\r\n   at Umbraco.Web.Editors.CurrentUserController.GetUserTours() in D:\\a\\1\\s\\src\\Umbraco.Web\\Editors\\CurrentUserController.cs:line 103\r\n   at lambda_method(Closure , Object , Object[] )\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass6_2.<GetExecutor>b__2(Object instance, Object[] methodParameters)\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__1.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---

It seems there's something wrong with the tours. I've reported this issue before but didn't get any answers.

Undid the changes and reverted to v8.5.3 and the site is working again.

Hopefully someone can help as otherwise I'll be stuck on v8.5.3 forever.