Happens all the time in the small-production-run solid-state world. Oversights in manufacturing like no heat-conducting paste between transistors and heat sinks, for example. Or a wave solder machine not properly set up for EU-required leadfree solder, so the solder joints on a circuit board start going bad after a while.
There’s some pretty sketchy tube stuff too ... I remember seeing bulky, heavy electrolytic capacitors "attached" to the chassis with RTV silicone goo ... and no bolts, clamps, or other hardware! From a highly reviewed European manufacturer that is still in business twenty years later. Or a well-known American manufacturer that omitted, or forgot, the required 10~100 uF decoupling/stabilization capacitors for the multiple 3-pin voltage regulators, so they sang happily in the 10 MHz range. Easily visible on an RF spectrum analyzer, but not easily seen on a scope.