I had this happen to my car as well. I also solved it.
The door would open, but then immediately close again while the charge light remained in its "ready" state... and more perplexing, I was still able to charge and Supercharge while it was trying to eat the cord constantly. I really didn't want this to continue and actually break something...
Since I was already well-immersed in tinkering with the car, I had the routine to do a complete shutdown/reset down to a science at this point. So that's what I did.
This is how you do a complete shutdown/reset. The "two-button reboot" does absolutely nothing for anything unrelated to the MCU, as it just reboots the screen. This, though, completely restarts all the car systems:
1) Open the frunk.
2) Lift the big plastic panel around the windshield wipers out of the way. It just snaps out, so just lift.
3) Get a 10mm socket or wrench, and loosen the negative terminal of the 12v battery quite a bit, so it'll loosely slide off - but more importantly, so it'll fully seat back on the post when you come back later. (Note, don't remove the cable from the connector - that's the other bolt - but rather loosen the clamp that holds it to the post on the battery)
4) Lift the negative terminal off the battery post. Swing the cable out of the way and hook it on something so it doesn't flop back onto the battery. Or have someone hold it.
5) Walk to the
passenger side rear door, and give a confused look as you open the door and the car is still powered up? Wuh? Yeah, the 12v battery isn't actually used for anything while the car is awake (idle/not in sleep mode). The entire car and all its accessories are powered by the PCS (power conversion system) built into the main battery, which you need to unplug next. Digest this information and pass it on to anyone that says "Sentry wears out the 12v battery"
6) There's a little rotating plastic latch under the lower lip of the rear seat on each side. You can lift both and remove the seat, or (more simply) just lift the passenger side of the seat, revealing a dense grey Styrofoam-like block.
7) Lift that block out of the way, noting which way it came out, so you can return it again in a few seconds.
8) There's a grey/black data connector there. Attack! To unplug it, there's a lever on the side. This lever should press/rotate outward and down towards the battery/floor to disengage it. When you unplug it, you'll hear a "clunk" as the car powers off.
9) Great, now push the top of that grey/black plug to reconnect it and lock the lever back where you found it.
10) Replace that foam block and click the seat back into place.
11) Take a few seconds to think how cool that is. Swear you'll tell at least 5 people that the 12v battery doesn't actually power anything, and they can be slightly more educated on electricity
(it powers the car when it's totally asleep, but other than that, all the 12v stuff is driven by the main battery and the PCS!)
12) Go back to the front and plug the 12v battery negative terminal back in. Make sure it's fully seated.
13) Screw it back tight again with that 10mm tool.
14) Replace the plastic shield, snap it down all around the edges so there's no gaps sticking out.
15) Close the frunk and hop back in the car so you can watch it boot back up.
16) Et voila, a complete reboot.
Really wish Tesla would just implement a "reboot the darn car" button, like they do during updates...!
But with this, my weird charging flap problem was fixed, and hasn't recurred since then.