Something I’ve personally noticed as someone who will perform a light disassemble before tossing an “broken” item.
The plug in oil heaters that look like radiators. Efficient, low cost. 3 now, total. The knob spins and I can no longer turn it on. Unplug. Unscrew. And a broken Dshaft knob falls out. They don’t make it obvious and easy to get to these knobs, you have to remove the large side panel without bothering the wires to get to a small panel to unscrew to get to the knobs. Then you have to find or make a Dshaft knob to fit, which isn’t easy.