WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
Condition
Fig 1: Identifying Transmission Cables And Levers
Courtesy of VOLVO CARS OF NORTH AMERICA.
Applies to M56/M58/M59 generally.
Possible Source
Faulty routing of the mechanical transmission cables to the levers.