Since we've updated from 7.5 to 7.10 we're experiencing some weird issues with our loadbalanced Umbraco solution with scheduled publishing. The logfile contains the following (after scheduling a site to be published at 14:40):

2018-07-12 14:40:44,475 [P4044/D4/T65] INFO  Umbraco.Core.Publishing.PublishingStrategy - Content 'TEST scheduled publishing' with Id '19391' has been published.
2018-07-12 14:40:44,611 [P4044/D4/T65] ERROR Umbraco.Core.Publishing.ScheduledPublisher - Error publishing node 19391
System.NullReferenceException: Object reference not set to an instance of an object.
at lambda_method(Closure , Object )
at NHibernate.Context.WebSessionContext.GetMap()
at NHibernate.Context.MapBasedSessionContext.get_Session()
at NHibernate.Context.CurrentSessionContext.HasBind(ISessionFactory factory)
at [](Boolean createNewScope, Boolean withTransaction)
at [](Boolean newPersistenceContext)
at [](Int32 contentId)
at []UpdateTemplateSearchProperties(IContent item, Boolean unPublished, Boolean isSaving)
at umbraco.content.DocumentCacheEventHandler.Invoke(Document sender, DocumentCacheEventArgs e)
at umbraco.content.FireAfterUpdateDocumentCache(Document sender, DocumentCacheEventArgs e)
at umbraco.content.UpdateDocumentCache(Document d)
at Umbraco.Web.Cache.PageCacheRefresher.Refresh(IContent instance)
at Umbraco.Core.Sync.ServerMessengerBase.DeliverLocal[T](ICacheRefresher refresher, MessageType messageType, Func`2 getId, IEnumerable`1 instances)
at Umbraco.Core.Sync.ServerMessengerBase.Deliver[T](IEnumerable`1 servers, ICacheRefresher refresher, MessageType messageType, Func`2 getId, IEnumerable`1 instances)
at Umbraco.Web.Cache.DistributedCache.Refresh[T](Guid factoryGuid, Func`2 getNumericId, T[] instances)
at Umbraco.Web.Cache.DistributedCacheExtensions.RefreshPageCache(DistributedCache dc, IContent[] content)
at Umbraco.Web.Cache.CacheRefresherEventHandler.ContentService_Published(IPublishingStrategy sender, PublishEventArgs`1 e)
at Umbraco.Core.Events.TypedEventHandler`2.Invoke(TSender sender, TEventArgs e)
at Umbraco.Core.Events.EventDefinition`2.RaiseEvent()
at Umbraco.Core.Events.ScopeEventDispatcher.ScopeExitCompleted()
at Umbraco.Core.Events.ScopeEventDispatcherBase.ScopeExit(Boolean completed)
at Umbraco.Core.Scoping.Scope.<>c__DisplayClass70_0.<RobustExit>b__1()
at Umbraco.Core.Scoping.Scope.TryFinally(Int32 index, Action[] actions)
at Umbraco.Core.Scoping.Scope.TryFinally(Int32 index, Action[] actions)
at Umbraco.Core.Scoping.Scope.RobustExit(Boolean completed, Boolean onException)
at Umbraco.Core.Scoping.Scope.Dispose()
at Umbraco.Core.Persistence.UnitOfWork.ScopeUnitOfWork.DisposeResources()
at Umbraco.Core.DisposableObjectSlim.Dispose(Boolean disposing)
at Umbraco.Core.DisposableObjectSlim.Dispose()
at Umbraco.Core.Services.ContentService.SaveAndPublishDo(IContent content, Int32 userId, Boolean raiseEvents)
at Umbraco.Core.Services.ContentService.Umbraco.Core.Services.IContentServiceOperations.SaveAndPublish(IContent content, Int32 userId, Boolean raiseEvents)
at Umbraco.Core.Services.ContentService.SaveAndPublishWithStatus(IContent content, Int32 userId, Boolean raiseEvents)
at Umbraco.Core.Publishing.ScheduledPublisher.CheckPendingAndProcess()
2018-07-12 14:40:44,616 [P4044/D4/T65] ERROR Umbraco.Web.Scheduling.ScheduledPublishing - Failed (see exception).
System.NullReferenceException: Object reference not set to an instance of an object.
at lambda_method(Closure , Object )
at NHibernate.Context.WebSessionContext.GetMap()
at NHibernate.Context.MapBasedSessionContext.get_Session()
at NHibernate.Context.CurrentSessionContext.HasBind(ISessionFactory factory)
at [](Boolean createNewScope, Boolean withTransaction)
at [](Boolean newPersistenceContext)
at [](Int32 contentId)
at []UpdateTemplateSearchProperties(IContent item, Boolean unPublished, Boolean isSaving)
at umbraco.content.DocumentCacheEventHandler.Invoke(Document sender, DocumentCacheEventArgs e)
at umbraco.content.FireAfterUpdateDocumentCache(Document sender, DocumentCacheEventArgs e)
at umbraco.content.UpdateDocumentCache(Document d)
at Umbraco.Web.Cache.PageCacheRefresher.Refresh(IContent instance)
at Umbraco.Core.Sync.ServerMessengerBase.DeliverLocal[T](ICacheRefresher refresher, MessageType messageType, Func`2 getId, IEnumerable`1 instances)
at Umbraco.Core.Sync.ServerMessengerBase.Deliver[T](IEnumerable`1 servers, ICacheRefresher refresher, MessageType messageType, Func`2 getId, IEnumerable`1 instances)
at Umbraco.Web.Cache.DistributedCache.Refresh[T](Guid factoryGuid, Func`2 getNumericId, T[] instances)
at Umbraco.Web.Cache.DistributedCacheExtensions.RefreshPageCache(DistributedCache dc, IContent[] content)
at Umbraco.Web.Cache.CacheRefresherEventHandler.ContentService_Published(IPublishingStrategy sender, PublishEventArgs`1 e)
at Umbraco.Core.Events.TypedEventHandler`2.Invoke(TSender sender, TEventArgs e)
at Umbraco.Core.Events.EventDefinition`2.RaiseEvent()
at Umbraco.Core.Events.ScopeEventDispatcher.ScopeExitCompleted()
at Umbraco.Core.Events.ScopeEventDispatcherBase.ScopeExit(Boolean completed)
at Umbraco.Core.Scoping.Scope.<>c__DisplayClass70_0.<RobustExit>b__1()
at Umbraco.Core.Scoping.Scope.TryFinally(Int32 index, Action[] actions)
at Umbraco.Core.Scoping.Scope.TryFinally(Int32 index, Action[] actions)
at Umbraco.Core.Scoping.Scope.RobustExit(Boolean completed, Boolean onException)
at Umbraco.Core.Scoping.Scope.Dispose()
at Umbraco.Core.Persistence.UnitOfWork.ScopeUnitOfWork.DisposeResources()
at Umbraco.Core.DisposableObjectSlim.Dispose(Boolean disposing)
at Umbraco.Core.DisposableObjectSlim.Dispose()
at Umbraco.Core.Services.ContentService.SaveAndPublishDo(IContent content, Int32 userId, Boolean raiseEvents)
at Umbraco.Core.Services.ContentService.Umbraco.Core.Services.IContentServiceOperations.SaveAndPublish(IContent content, Int32 userId, Boolean raiseEvents)
at Umbraco.Core.Services.ContentService.SaveAndPublishWithStatus(IContent content, Int32 userId, Boolean raiseEvents)
at Umbraco.Core.Publishing.ScheduledPublisher.CheckPendingAndProcess()
at Umbraco.Web.Scheduling.ScheduledPublishing.PerformRun()
2018-07-12 14:40:48,618 [P4044/D4/T55] INFO  umbraco.content - Save Xml to file...
2018-07-12 14:40:48,942 [P4044/D4/T55] INFO  umbraco.content - Saved Xml to file.

Has anyone ever experienced anything like that? The exception seems to be thrown at CurrentSessionContext (NullReferenceException) when I try to debug it locally.

It might be related to this fix: http://issues.umbraco.org/issue/U4-10150

I've already tried some kind of workaround with an own session context as mentioned here: https://stackoverflow.com/questions/5854238/nhibernate-session-management-strategy-for-web-application-with-background-worke

This seemed to be working at first glance, but somehow it isn't anymore. I'm freaking out about this error ... can anyone please give me a hint/suggestion what to do?