Probably the same problem like the seat back twist, the inner core of the bowden cable is too long and has to be shortened. Go to my website below there is a link to Gale's page, he has a write up. Also Winfred has an excellent write up with pics. Use the search for it, can't find it at the moment.

Recently solved a similar problem in my friends car, the inner part of the bowden cable was completely twisted and broken.
Bowden cables can be bought from the dealer, but better check beforehand what is written on it for the length of the cable. On E32 for example there were 2 makers of seats for BMW and the lenghth of the bowden cables it slightly different.