I had a number of people who thought that they could by a whole set of new tubes and stick them into a TV or radio and that it would fix it. They also thought that we should take the tubes back if it didn't work.
A portable series string TV came into the shop. I was walking by as the main TV tech was taking the back off. There was a shiny new .47 uF Sprague orange drop where the 20 watt .47 ohm fusible resistor should be. I pointed to it an d laughed as I told him what they had done. Of course, he didn't believe me, because I was "merely" the head of the commercial sound division. 30 seconds later he was yelling around the corner, "Do we have any .47 fusibles in stock?"
Or the ones who felt the same way because you gave the weak CRT a shot to rejuvenate it and reset the gray scale.
Two years before I was drafted, and a few more years scattered between working in Broadcast, CATV, Commercial Sound, Computer repair and electronics manufacturing.
You wouldn't believe some of the crap that happens on the production line with a lot of hand assembly. Large computer grade electrolytics installed backwards and some idiot just shoves the connector into the test fixture and hits it with full line voltage and complains that the can hit him when it exploded. 288 pin ICs turned 90 or 180 degrees and not caught by QC. Surface mount tantalum capacitors installed backwards and not found till the equipment was in the field, after the equipment caught on fire.
And then, there was the nasty repairs done to broadcast equipment, and not documented. Its no fun to try to get back on the air, only to find some hack had jury rigged something that caused more damage and you need to get back on the air but it will take all day, rather than 15 minutes.