What can be the cause of these Oracle ORA-00600 errors?

These errors appear sporadically and we have to do alter system flush buffer_cache; to get rid of them

   at OracleInternal.ServiceObjects.OracleConnectionImpl.VerifyExecution(Int32& cursorId, Boolean bThrowArrayBindRelatedErrors, SqlStatementType sqlStatementType, Int32 arrayBindCount, OracleException& exceptionForArrayBindDML, Boolean& hasMoreRowsInDB, Boolean bFirstIterationDone)
   at OracleInternal.ServiceObjects.OracleCommandImpl.ExecuteReader(String commandText, OracleParameterCollection paramColl, CommandType commandType, OracleConnectionImpl connectionImpl, OracleDataReaderImpl& rdrImpl, Int32 longFetchSize, Int64 clientInitialLOBFS, OracleDependencyImpl orclDependencyImpl, Int64[] scnForExecution, Int64[]& scnFromExecution, OracleParameterCollection& bindByPositionParamColl, Boolean& bBindParamPresent, Int64& internalInitialLOBFS, OracleException& exceptionForArrayBindDML, OracleConnection connection, OracleLogicalTransaction& oracleLogicalTransaction, IEnumerable`1 adrianParsedStmt, Boolean isDescribeOnly, Boolean isFromEF)
   at Oracle.ManagedDataAccess.Client.OracleCommand.ExecuteReader(Boolean requery, Boolean fillRequest, CommandBehavior behavior)
   at Oracle.ManagedDataAccess.Client.OracleCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.Reader(DbCommand command, DbCommandInterceptionContext interceptionContext)
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryInternal[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)
   at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass65`1.<ExecuteStoreQueryReliably>b__64()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
   at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass65`1.<ExecuteStoreQueryReliably>b__63()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryReliably[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQuery[TElement](String commandText, ExecutionOptions executionOptions, Object[] parameters)
   at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at ... some methods.....<Get>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.TaskHelpersExtensions.<CastToObject>d__3`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Filters.AuthorizationFilterAttribute.<ExecuteAuthorizationFilterAsyncCore>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Web.Http.Controllers.ExceptionFilterResult.<ExecuteAsync>d__0.MoveNext()
---> (Inner Exception #0) Oracle.ManagedDataAccess.Client.OracleException (0x80004005): ORA-00600: internal error code, arguments: [kaf_typed_stuff:invalid locator version], [46798], [], [], [], [], [], [], [], [], [], []
   at OracleInternal.ServiceObjects.OracleConnectionImpl.VerifyExecution(Int32& cursorId, Boolean bThrowArrayBindRelatedErrors, SqlStatementType sqlStatementType, Int32 arrayBindCount, OracleException& exceptionForArrayBindDML, Boolean& hasMoreRowsInDB, Boolean bFirstIterationDone)
   at OracleInternal.ServiceObjects.OracleCommandImpl.ExecuteReader(String commandText, OracleParameterCollection paramColl, CommandType commandType, OracleConnectionImpl connectionImpl, OracleDataReaderImpl& rdrImpl, Int32 longFetchSize, Int64 clientInitialLOBFS, OracleDependencyImpl orclDependencyImpl, Int64[] scnForExecution, Int64[]& scnFromExecution, OracleParameterCollection& bindByPositionParamColl, Boolean& bBindParamPresent, Int64& internalInitialLOBFS, OracleException& exceptionForArrayBindDML, OracleConnection connection, OracleLogicalTransaction& oracleLogicalTransaction, IEnumerable`1 adrianParsedStmt, Boolean isDescribeOnly, Boolean isFromEF)
   at Oracle.ManagedDataAccess.Client.OracleCommand.ExecuteReader(Boolean requery, Boolean fillRequest, CommandBehavior behavior)
   at Oracle.ManagedDataAccess.Client.OracleCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Entity.Infrastructure.Interception.InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target, Func`3 operation, TInterceptionContext interceptionContext, Action`3 executing, Action`3 executed)
   at System.Data.Entity.Infrastructure.Interception.DbCommandDispatcher.Reader(DbCommand command, DbCommandInterceptionContext interceptionContext)
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryInternal[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)
   at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass65`1.<ExecuteStoreQueryReliably>b__64()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
   at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass65`1.<ExecuteStoreQueryReliably>b__63()
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQueryReliably[TElement](String commandText, String entitySetName, ExecutionOptions executionOptions, Object[] parameters)
   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteStoreQuery[TElement](String commandText, ExecutionOptions executionOptions, Object[] parameters)
   at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()<---