My 1987 300D/124 (~290K miles) has an inop turbo. This is the fifth turbo on this car. I do not seem to read anyone here with such frequent need to replace/rebuild the turbo. The actuator was not working and the waste gate was also inop. Any ideas as to why this would be happening so frequently?

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K