My phone had "broken" - the bottom speaker made a terrible static/garbage sound whenever an app enabled media playback. (Phone calls worked alright, those just play out the top speaker.) I assumed that a hardware connection had broken, and that the speaker was toast.
Ordered new phone. Wait several days, tolerating the hissing.
This morning, with my new phone arriving today, my old phone got a monthly patch update and rebooted. The speaker was fixed. No more crackle. It was software. A restart had fixed it.
I assumed that there was no way that static could have been caused by a software fault. I assumed so hard that I didn't restart the phone. Ooooh. Touche.
Well, a 2.5-year upgrade cycle isn't awful, relative to my "last 3 years this time" goal.