Probably the ignition key cylinder. This needs tended to soon because in a short time you will not be able to turn it at all which will neccesitate drilling out the cyl and lock pin! What you did was jumper around the neutral safety switch. Which has nothing to do with the mechanical ignit. switch lock cylinder. Within the cylinder are a number of "pins" that fall in specific height to match your specific key allowing it to rotate, one or more of them is worn enough that it is jambed between the key and the bore of the cylinder.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.