Also if I debug I don't get the issue, only when the code is executing as standard

It seems popping a Thread.Sleep(500) fixes the problem so I think something weird is going on with the caching of the addresses

It works for me (on 11.8.2), I can get contact addresses many times without exception.

var userPrinciple = ServiceLocator.Current.GetInstance<IUserImpersonation>().CreatePrincipal("admin@example.com");
var customerContact = userPrinciple.GetCustomerContact();
var addresses = customerContact.ContactAddresses.ToList();

I'm not sure about UserImpersonationService.

Thanks, something weird went on when pasting, I'm using IUserImpersonation same as yourself it's just injected. That's effectivly the same code I'm running just with the injection differences, although it's running in a task so is in a separate thread which may impact it, although the small thread delay seems to be working

I think the task running in separate thread causes smthing in BusinessManager.Execute() (which is quite complex)

Could you give more info about which variable is null?

There's nothing in the exception as it's a null reference that tells me which object is null although I've had similar issues with a previous version of the code which just stopped working and that was having issues around the HttpContext although I'm passing through CallContext.HostContext = context; with a pointed to the active context with the code that's running. At the moment all I have is the error I've pasted above, there was little more in the exception detail. 

You could may be able to replicate what I'm doing by running your code you posted in a task calling the method with that code in with

Task.Run(() =>
{
CallContext.HostContext = context;
METHOD
});

In my case this code is being executed in the in the authentication steps of after login

            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
                Provider = new CookieAuthenticationProvider
                {
                    // Enables the application to validate the security stamp when the user logs in.
                    // This is a security feature which is used when you change a password or add an external login to your account.
                    OnValidateIdentity = SecurityStampValidator.OnValidateIdentity<ApplicationUserManager<ApplicationUser>, ApplicationUser>(
                        validateInterval: TimeSpan.FromMinutes(30),
                        regenerateIdentity: (manager, user) => manager.GenerateUserIdentityAsync(user)),
                    OnResponseSignedIn = OnResponseSignedIn
                },
                SlidingExpiration = true,
                ExpireTimeSpan = TimeSpan.FromMinutes(30)
            });

private void OnResponseSignedIn(CookieResponseSignedInContext cookieResponseSignedInContext)
        {
                var context = System.Web.HttpContext.Current;
                Task.Run(() =>
                {
                    CallContext.HostContext = context;
                    METHOD;
                });
        }

It works for me :)

        public void Configuration(IAppBuilder app)
        {
            app.AddCmsAspNetIdentity<SiteUser>(new ApplicationOptions
            {
                ConnectionStringName = _connectionStringHandler.Commerce.Name
            });

            app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
                LoginPath = new PathString("/Login"),
                Provider = new CookieAuthenticationProvider
                {
                    OnValidateIdentity = SecurityStampValidator.OnValidateIdentity<ApplicationUserManager<SiteUser>, SiteUser>(
                        validateInterval: TimeSpan.FromMinutes(30),
                        regenerateIdentity: (manager, user) => manager.GenerateUserIdentityAsync(user)),
                    OnApplyRedirect = context => context.Response.Redirect(context.RedirectUri),
                    OnResponseSignOut = context => context.Response.Redirect(UrlResolver.Current.GetUrl(ContentReference.StartPage)),
                    OnResponseSignedIn = OnResponseSignedIn
                },
                SlidingExpiration = true,
                ExpireTimeSpan = TimeSpan.FromMinutes(30)
            });

            app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);
            app.UseTwoFactorSignInCookie(DefaultAuthenticationTypes.TwoFactorCookie, TimeSpan.FromMinutes(5));
            app.UseTwoFactorRememberBrowserCookie(DefaultAuthenticationTypes.TwoFactorRememberBrowserCookie);
        }

        private void OnResponseSignedIn(CookieResponseSignedInContext cookieResponseSignedInContext)
        {
            var context = System.Web.HttpContext.Current;

            Task.Run(() =>
            {
                CallContext.HostContext = context;

                var userPrinciple = ServiceLocator.Current.GetInstance<IUserImpersonation>().CreatePrincipal("admin@example.com");
                var customerContact = userPrinciple.GetCustomerContact();
                var addresses = customerContact.ContactAddresses.ToList();
            });
        }

Note it seems to work the first few times but after a few hits then it's breaking. The delay I think is working so I guess I'll go with that