HDMI port replacement
Console runs, TV gets nothing.
Xbox has a long history with heat and people remember it, so a console that's suddenly loud makes owners nervous.
Usually it's much less dramatic than that: dust in the heatsink and thermal paste that's gone hard.
It's still worth acting on. Heat is cumulative, and the damage it does creeps up on you.
Everyone knows about dust, and a good clean does help. What people miss is the thermal compound between the chip and the heatsink — after a few years it dries out and stops transferring heat properly, and no amount of compressed air fixes that.
The Series S is worth a particular mention here. Small case, tight airflow, and it runs warmer than its size suggests, so it benefits from a service sooner than you'd expect.
You can for a while. The reason not to is that sustained heat degrades the solder under the main chip, and that repair costs many times what a clean and repaste does.
Console runs, TV gets nothing.
Front or rear port stopped working.
Controller only charges at a certain angle.
Dead, or it powers up for a second and quits.
Grinding, ejecting, or a disc stuck inside.
Aim drifts, sticky buttons, dead triggers.