AVOption with the MOTU Midi Timepiece

[baxter]

Protools with AV Option ver 5.0.1

We are using the MOTU Midi Timepiece for locking (instead of the USD) along with a VSD.

Black burst is given to the VSD and the MTP Video reference input.
Slave clock (256x clock) from the VSD is given to the Audio Interfaces.
Timecode is coming into the MTP.

On the PT the session is setup for 25 frames and 48k sample rate.
Like wise on the MTP the Sync is set to Video/LTC (we have tried only LTC and even LTC Quiklock), frame rate 25 fps and Fs is 48k.
The timecode freewheel on the PT and MTP is 4 frames.
No offset is set on the MTP.

When we grab picture from a VTR the video and picture are bang on in sync, however the TC on Protools is lagging with respect to the burnt in TC seen of the Video by 6 frames.

When we grab only picture from a VTR and then grab the audio, both are bang on in sync, however the TC on Protools is lagging with respect to the burnt in TC seen of the Video by 6 frames.

Now if we were to grab just audio from a Hi8 machine or a timecode DAT we find that the audio is starting at the correct point. There is no mismatch in the PT timecode, We could identify this by using material that had material referenced to a timecode that we were familiar with.

Yes if we use the USD then there is no difference in the timecode between the PT and burnt in TC seen on the video screen.

Understandably USD is only approved unit to be used with the AV Option, why does one face a problem with the MTP?

Why is there is a fixed 6 frames difference between the timecode off the PT versus burnt in TC seen on the video screen?
Why is the audio in sync with the picture grabbed off the VTR? (There is no drift)