Has anyone successfully upgraded a 6.2.6 site to 7.6.3? I've followed the various upgrade docs dotted around here but have hit a wall with regards to Umbraco forms (or contour in my 6.2.6 deployment). The site throws a Sql exception (stack trace below) on startup. I'm conscious of the fact that contour has been replaced by Umbraco forms. Not sure on the best way forward. Is it even possible to jump directly from 6.2.6 to 7.6.3 or should I first go to an earlier 7 version and then migrate up from there?

Stack trace below:

[SqlException (0x80131904): New transaction is not allowed because there are other threads running in the session.] System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action1 wrapCloseInAction) +2442598 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action1 wrapCloseInAction) +5766516 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) +285 System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) +4162 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +69 System.Data.SqlClient.TdsParser.TdsExecuteTransactionManagerRequest(Byte[] buffer, TransactionManagerRequestType request, String transactionName, TransactionManagerIsolationLevel isoLevel, Int32 timeout, SqlInternalTransaction transaction, TdsParserStateObject stateObj, Boolean isDelegateControlRequest) +799 System.Data.SqlClient.SqlInternalConnectionTds.ExecuteTransactionYukon(TransactionRequest transactionRequest, String transactionName, IsolationLevel iso, SqlInternalTransaction internalTransaction, Boolean isDelegateControlRequest) +572 System.Data.SqlClient.SqlInternalConnectionTds.ExecuteTransaction(TransactionRequest transactionRequest, String name, IsolationLevel iso, SqlInternalTransaction internalTransaction, Boolean isDelegateControlRequest) +137 System.Data.SqlClient.SqlInternalConnection.BeginSqlTransaction(IsolationLevel iso, String transactionName, Boolean shouldReconnect) +254 System.Data.SqlClient.SqlConnection.BeginTransaction(IsolationLevel iso, String transactionName) +147 System.Data.SqlClient.SqlConnection.BeginDbTransaction(IsolationLevel isolationLevel) +58 System.Data.Common.DbConnection.BeginTransaction(IsolationLevel isolationLevel) +12 StackExchange.Profiling.Data.ProfiledDbConnection.BeginDbTransaction(IsolationLevel isolationLevel) +33 System.Data.Common.DbConnection.System.Data.IDbConnection.BeginTransaction(IsolationLevel isolationLevel) +12 Umbraco.Core.Persistence.Database.BeginTransaction(IsolationLevel isolationLevel) +58 Umbraco.Core.Scoping.Scope.getDatabase() +193 Umbraco.Core.Persistence.UnitOfWork.ScopeUnitOfWork.getDatabase() +15 Umbraco.Core.Persistence.Repositories.UserRepository.PerformGet(Int32 id) +285 Umbraco.Core.Cache.DefaultRepositoryCachePolicy2.Get(TId id, Func2 performGet, Func2 performGetAll) +110 Umbraco.Core.Persistence.Repositories.RepositoryBase2.Get(TId id) +243 Umbraco.Core.Services.UserService.GetUserById(Int32 id) +68 umbraco.BusinessLogic.User.SetupUser(Int32 ID) +42 umbraco.BusinessLogic.User..ctor(Int32 ID) +53 Umbraco.Forms.Core.Configuration.ensureSettingsDocument() +401 Umbraco.Forms.Core.Configuration.get_UmbracoFormsConfig() +143 Umbraco.Forms.Core.<>cDisplayClass3.2() +64 umbraco.cms.businesslogic.cache.<>cDisplayClass11.<GetCacheItem>b__0() +10 Umbraco.Core.<>c__DisplayClass81.6() +10 Umbraco.Core.Cache.<>cDisplayClass1.0() +31

[Exception: Exception while creating a value.] Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, CacheDependency dependency) +1003 Umbraco.Core.CacheHelper.GetCacheItem(String cacheKey, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, CacheDependency cacheDependency, TimeSpan timeout, Func1 getCacheItem) +214 umbraco.cms.businesslogic.cache.Cache.GetCacheItem(String cacheKey, Object syncLock, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, CacheDependency cacheDependency, TimeSpan timeout, GetCacheItemDelegate1 getCacheItem) +199 umbraco.cms.businesslogic.cache.Cache.GetCacheItem(String cacheKey, Object syncLock, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, TimeSpan timeout, GetCacheItemDelegate1 getCacheItem) +79 umbraco.cms.businesslogic.cache.Cache.GetCacheItem(String cacheKey, Object syncLock, CacheItemRemovedCallback refreshAction, TimeSpan timeout, GetCacheItemDelegate1 getCacheItem) +76 Umbraco.Forms.Core.Services.CacheService.GetCacheItem(String cacheKey, Object syncLock, TimeSpan timeout, GetCacheItemDelegate1 getCacheItem) +114 Umbraco.Forms.Core.Configuration.GetSetting(String key) +205 Umbraco.Forms.Core.FormSettings..ctor() +68 Umbraco.Forms.Core.Form.Create() +135 Umbraco.Forms.Core.Form.CreateFromDataReader(IRecordsReader reader) +92 Umbraco.Forms.Data.Storage.<>c__DisplayClass6.<GetAllForms>b__4() +56 umbraco.cms.businesslogic.cache.<>c__DisplayClass11.

[Exception: Exception while creating a value.] Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Func1 getCacheItem, Nullable1 timeout, Boolean isSliding, CacheItemPriority priority, CacheItemRemovedCallback removedCallback, CacheDependency dependency) +1003 Umbraco.Core.CacheHelper.GetCacheItem(String cacheKey, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, CacheDependency cacheDependency, TimeSpan timeout, Func1 getCacheItem) +214 umbraco.cms.businesslogic.cache.Cache.GetCacheItem(String cacheKey, Object syncLock, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, CacheDependency cacheDependency, TimeSpan timeout, GetCacheItemDelegate1 getCacheItem) +199 umbraco.cms.businesslogic.cache.Cache.GetCacheItem(String cacheKey, Object syncLock, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, TimeSpan timeout, GetCacheItemDelegate1 getCacheItem) +79 umbraco.cms.businesslogic.cache.Cache.GetCacheItem(String cacheKey, Object syncLock, CacheItemRemovedCallback refreshAction, TimeSpan timeout, GetCacheItemDelegate1 getCacheItem) +76 Umbraco.Forms.Core.Services.CacheService.GetCacheItem(String cacheKey, Object syncLock, TimeSpan timeout, GetCacheItemDelegate`1 getCacheItem) +114 Umbraco.Forms.Data.Storage.FormStorage.GetAllForms() +503 Umbraco.Forms.CodeFirst.FormManager.SynchronizeForm(Type typeForm) in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.CodeFirst\FormBuilder\FormManager.cs:214 Umbraco.Forms.CodeFirst.FormManager.SynchronizeForms() in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.CodeFirst\FormBuilder\FormManager.cs:201 Umbraco.Forms.CodeFirst.FormManager.Synchronize() in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.CodeFirst\FormBuilder\FormManager.cs:24 Umbraco.Forms.CodeFirst.UmbracoManager.Synchronize() in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.CodeFirst\UmbracoManager.cs:36 Umbraco.Forms.CodeFirst.UmbracoManager.SynchronizeIfNotSynchronized() in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.CodeFirst\UmbracoManager.cs:21 Umbraco.Forms.CodeFirst.ContourFormBuilderHttpModule.context_BeginRequest(Object sender, EventArgs e) in f:\TeamCity\buildAgent\work\fd622d7f786e1305\Umbraco.Forms.CodeFirst\ContourFormBuilderHttpModule.cs:27 System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +141 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +69