Replace all bulbs in pairs with Osram (my preference) or other OEM bulbs. If you replace just one of a pair and the current draw is different that the one you left if, the lamp goes on.
The Benz isn't as bad and the Volvo -- took three tries to get a pair of brake lamp bulbs that wouldn't set the silly thing off. That's why I buy Osram -- they were the only ones to work.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!