Service Broker: Procedure is not executed

Hi there. I have some troubles with SB. I created stored procedure and the all SB part, however the message appears in the queue but the procedure is executed only sometimes. It executed the first time and executed after some times later. What is wrong?

The code I use.

CREATE PROCEDURE dbo.sb_test

AS
  select 'abrakadabra'
  DECLARE @h UNIQUEIDENTIFIER;
  DECLARE @messageTypeName SYSNAME;
  DECLARE @payload VARBINARY(MAX);
  WAITFOR(RECEIVE TOP(1)
    @h = conversation_handle,
    @messageTypeName = message_type_name,
    @payload = message_body
    FROM SBReceiveQueue), TIMEOUT 1000;

  INSERT INTO test(a) values(GETDATE());
GO

There is the code for SB part:

-- Create Message Type
CREATE MESSAGE TYPE SBMessage
VALIDATION = NONE
GO
-- Create Contract
CREATE CONTRACT SBContract
(SBMessage SENT BY INITIATOR)
GO
-- Create Send Queue
alter QUEUE SBSendQueue
    WITH STATUS=ON,
    ACTIVATION (
        PROCEDURE_NAME = dbo.sb_test,
        MAX_QUEUE_READERS = 1,
        EXECUTE AS SELF 
         ) ;

GO
-- Create Receive Queue
CREATE QUEUE SBReceiveQueue
GO
-- Create Send Service on Send Queue
CREATE SERVICE SBSendService
ON QUEUE SBSendQueue (SBContract)
GO
-- Create Receive Service on Recieve Queue
CREATE SERVICE SBReceiveService
ON QUEUE SBReceiveQueue (SBContract)
GO
-- Begin Dialog using service on contract
DECLARE @SBDialog uniqueidentifier
DECLARE @Message NVARCHAR(128)
BEGIN DIALOG CONVERSATION @SBDialog
FROM SERVICE SBSendService
TO SERVICE 'SBReceiveService'
ON CONTRACT SBContract
WITH ENCRYPTION = OFF

SET @Message =  N'AAAAAAAAAAA'; --  CAST(GETDATE() AS VARCHAR);
SEND ON CONVERSATION @SBDialog
MESSAGE TYPE SBMessage (@Message)
GO