Timeout Expired in ...TestCaseManager::TestCaseFolder_GetParents

Hello Inflectra support team, 
Recently a significant amount of timeout errors have been registered in the Spirateam log. 

An error occurred while executing the command definition. See the inner exception for details.
In APPLICATION.Web.Services.Ajax.Json.SpiraErrorHandler::ProvideFault:

Messages:
An error occurred while executing the command definition. See the inner exception for details. [System.Data.EntityCommandExecutionException]
Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding. [System.Data.SqlClient.SqlException]
The wait operation timed out [System.ComponentModel.Win32Exception]

Stack Trace:
at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior)
at System.Data.Objects.ObjectContext.CreateFunctionObjectResult[TElement](EntityCommand entityCommand, ReadOnlyMetadataCollection`1 entitySets, EdmType[] edmTypes, MergeOption mergeOption)
at System.Data.Objects.ObjectContext.ExecuteFunction[TElement](String functionName, MergeOption mergeOption, ObjectParameter[] parameters)
at APPLICATION.Business.SpiraTestEntities.TestCase_RetrieveParentFolders(Nullable`1 projectId, Nullable`1 folderId, Nullable`1 isIncludeSelf)
at APPLICATION.Business.TestCaseManager.TestCaseFolder_GetParents(Int32 projectId, Int32 testFolderId, Boolean includeSelf)
at APPLICATION.Web.Services.Ajax.TestSetTestCaseService.RetrieveNameDesc(Nullable`1 projectId, Int32 testSetTestCaseId, Nullable`1 displayTypeId)
at SyncInvokeRetrieveNameDesc(Object , Object[] , Object[] )
at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]& outputs)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet) 

I tried to fix the problem by rebuilding indexes, but it had no effect. 

Spirateam version 6.2.0.1 
MS SQL Server 2014 Standard (64)
Windows Server 2019 Standard edition, 24 GB,  processors 6, Intel Xeon 4216  2.1 GHz