Concerning the Rebuilding Industry. One of their problems is getting Cores that are in good enough shape that they can be rebuilt.

In the case of Mercedes even if you include the Gassers there just is not and many Cores out there for them to try to rebuild. And, as time passes less and less of those Cores in are in good enough condition to be rebuilt.

so they are rebuilding a lot of marginal Parts that the give a warranty on but they are betting something will happen like you losing the Paperwork to return them, you sell the Car, like Me you might not even remember where you bought the rebuilt one from and so on. So the odds are on the side of them not having to warrant a crappy rebuild job.

Then on top of that they are sending those parts overseas to be rebuilt.
If the Overseas Rebuilder receives 5,000 items to be rebuilt the Rebuilder is going try to send all 5,000 back. That means they are not going to be so picky in deciding what they are actually going to rebuild.

Then there is the Overseas Workers. Likely taught enough to do the Job but might be getting only for each piece they complete.
I am pretty sure the Worker is not going to get blamed on some bad Unit He puts out since it is outside of His or Her country and not worth tracing back to the Worker.

Some Members have said that they won't work on the Master Cylinders or the Calipers due to safety. But, the training of the People who do the rebuilding in a Factory of those items is unknown.

__________________
84 300D, 82 Volvo 244Gl Diesel