When an edit is started the positions of all slaved transports are
checked against the transport lock.
If there is a mismatch between the film position and the main recorder
position, an error panel will appear.
If this is the start of a new film project, then select New
sequence. This is the same as using the TRANSPORT button.
If this is a new reel for the same film and the sequence should be
maintained then select Old sequence.
There is also a 
option in
the edit setup panel.
If this is On then any Vtr In points will be trimmed
back to match the existing film sequence on tape.
If a Vtr In is entered from the numeric keypad, then this will not be trimmed.