Not familiar with this particular option so some of the thoughts may not apply. Motors, though, can all reach the limit on brush wear or develop shorts internally. If enough brush carbon ends up in the wrong places, that could also cause a short. The seat movement drive gears or cable may have developed a rough spot, which can overload the motor when passing that point. That could potentially blow a fuse. Could dirt or carpet loops have gotten caught in the seat track?

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150