Pro Audio Support

Q:
When slaving Pro Tools (with USD) to a 2" deck:-If I start the 2" at the top of the song and monitor back both PT and 2", they phase, meaning they're locked. But if I stop the tape, then start again from anywhere besides the top of the song, the 2 are clearly not in sync.
 
A:
-The USD needs to be set to "LTC" for both Clock Reference and Positional Reference.