If you shut off the car with the doors locked, then try to unlock them will they unlock? You likely have a vacuum leak in the system which allows the vacuum to leak while the doors are locked so there is no vacuum left to un-lock them after the car has been sitting. Buy a Mity-vac and start testing!

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine