PMDG 747 TRC Course 4 problems

Hi Guys,

I am practising the PMDG type rating course 4..I have never faced this problem before..Here are the steps that i follow:

1) Select Clb-2 for the climb thrust in the FMC.
2) Set brakes to RTO
3) Bring up thrust to 70%
4) Hit TOGA.
5) At Vr I rotate
6) As soon as V2 callout happens the plane starts honking...

I have cheked for the possibility of tailstrike but there is no tail strike..I always face this problem when I restart the lesson with autopilot engaged from prev flight lesson..I mean i fly the lesson and engage the autopilot at 1000 ft AGL and level out at 5000 ft.If this is the first time I am flying after starting FS then there is no honking sound after rotation.
But after flying the lesson on autopilot and then restarting the lesson it starts honking at V2 callout...The same does not happen if i don't fly the previous TRC 4 course on autopilot..Many a times i just rotate the plane and climb manually to 1000 ft and then restart..But i don't face this problem after doing this..It is only when i have put the plane on autopilot and then restarted the lesson...

It never happened before...I have tried various combinations to see what is causing this problem and arrived at the conclusion which i have written above...I also tried under rotating the plane..But if it is the first flight for TRC4 then it is fine or restart from prev flight(without autopilot).If you need any further info then please let me know..Will take a video of it and post...