Ive done the oil change issue before too. Forgot to put the oil pan plug back in and dumped a lot of oil onto the driveway that day, and had to wait for a ride to get some more. Never made that mistake again.
Now for one more, I had my brakes done at a local shop once, because i was out of time and we were about to go on tour the next morning. So i dropped it off on the way to work, paid up front, walked to work and picked it up at the end of the night. The next day on the way out of town, it sounded like my front wheel had loose lugnuts. So we get out and check everything. All tight! A few miles later another loud thump. This time it sounded like the rear axle was popping. It wasnt regular so we kept trying to pay attention to it and tell where it was coming from. Finally. we pulled into a parking lot and had one person drive back and forth and we all watched the wheels. Then we saw it. The drivers rear wheel looked like it was hitting an invisible rock. Took the wheel off and the brakes were shot. He forgot to put a retaining clip on and pretty much two pads, two springs, one rivet, star adjuster, and the e-brake clip were all shot, as was my drum. we had to remove it all and keep going for 3 days before we could get the parts to fix it in a Target parking lot. Long story short (too late). ... this was from a professional mechanic. We all forget something sometime.

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1980 300D