I would check both trunk wire looms for broken wires, so check the looms on left and right side. Here some pics
Pics
Courtesy of the Japanese E34 repair community, trunk lid wire loom repair
http://dd.jpn.org/BMW_HP/20100501/index.shtml
http://dd.jpn.org/BMW_HP/20090410/index.shtml
Germany/Austria
http://de.tinypic.com/view.php?pic=2...7#.UzlqZGe9KUk
http://de.tinypic.com/view.php?pic=v...7#.Uzlqqme9KUk
and here in German language which wire color is for which part
http://de.tinypic.com/view.php?pic=j...7#.Uzlq22e9KUk
http://de.tinypic.com/view.php?pic=2...7#.UzlrFGe9KUk
http://de.tinypic.com/view.php?pic=x...7#.UzlrMWe9KUk
http://de.tinypic.com/view.php?pic=r...7#.UzlrXGe9KUk
how to remove the trunk shock
http://de.tinypic.com/view.php?pic=o...7#.UzlrfGe9KUk
more wire fixing
http://de.tinypic.com/view.php?pic=1...7#.UzlrnWe9KUk
http://de.tinypic.com/view.php?pic=q...7#.UzlruWe9KUk
http://de.tinypic.com/view.php?pic=v...7#.Uzlr0We9KUk
http://de.tinypic.com/view.php?pic=3...7#.Uzlr7We9KUk
http://de.tinypic.com/view.php?pic=2...7#.UzlsA2e9KUk
http://de.tinypic.com/view.php?pic=2...7#.UzlsIme9KUk