Headlights and brake lights going out intermittently

About a year ago, I turned my S5 on and all of the lights started going out one after another until all the headlights were dark (first DRL, then turn signals, then high and low beams, one by one). The navi screen wouldn’t turn on and the right brake light wasn’t working either. I made an appointment to take it to the dealer (that happens to be far away) two days later but when I turned it on to drive it to the dealer a couple days later, everything was working fine again, so I didn’t go (stupid, I know).

Everything worked perfectly until a couple weeks ago. It started with the center brake light - it would work for a couple minutes after I turned the car on and then go out after applying the brakes (accompanied by a warning indicator saying the center brake light failed). Then, a few days later, the right low beam/high beam light indicator went on. I got out and checked and sure enough, the DRL was on, but the bulb was not. I turned the lights off and on again and the bulb fired, stayed on for a couple minutes, and then went off again. This stopped for a couple days but restarted this week and has continued since. Then today, the left DRL went out completely and the right front turn signal (in the headlight assembly) is out when the car is on. Oddly though, when I turn the car off, the right front turn signal will flash (when locking the car) and actually stays on permanently even after the car is off (the car has been off now for two hours and the right front turn signal is still constantly on - see photo).

Also, a few of the center console lights - that illuminate the gearshift letters (P, R, N, D, etc.) And a couple nearby buttons have been out this entire time, as well.

Any ideas what is happening? At first, I thought something happened to the headlight ballast (corrosion, moisture, etc.), After reading forum posts where people has similar intermittent issues caused by ballast failure. However now that it’s happening simultaneously to numerous disparate systems (left DRL, right L/H beam, right turn signal, center brake light, console lights), it seems more likely that it’s a higher-level issue, like power supply or current, or something that could affect all of the electronics? Someone please help! Is there a fuse box I can check? What else might it be?

[notes: car is a 2014 S5 3.0 turbocharged engine, has 45k miles, has never been in an accident or even a fender bender, no body work, no aftermarket work, never seen snow, garaged most of the time, never any problems other than this, etc.]