Now playing: Watch this: How to fix your Nintendo Joy-Con connectivity issues

When you're playing Zelda with your new Nintendo Switch on your luxuriously large TV, does Link tend to run off cliffs like a damn lemming because your left controller suddenly stopped working?

It's colloquially known as the "left Joy-Con desync issue." It's been one of the biggest issues plaguing some early Switch reviewers and consumers. But it looks like Nintendo has discovered how to fix it.

First, the bad news: It's a hardware issue, so there's no point waiting around for a software update, or following Nintendo's suggestions to maybe never use your Switch near aquariums or microwaves or any wireless device ever made. (I wish I were joking.)

But here's the good news: Nintendo fixed my faulty Joy-Con in under a week. And the process was just about the best electronics customer service I've ever experienced.

The most interesting part: The fix involves a tiny new piece of "hardware," which I can prove with before-and-after pictures of my repaired Joy-Con.

There's also a possibility that Nintendo has already fixed the hardware at the source, based on a new standalone Joy-Con I purchased from Amazon. But the company isn't confirming anything.

Here's everything we know so far.

The fully repaired Joy-Con: Before and after

The Joy-Con desync issue occurs when you're using it wirelessly. It doesn't affect gameplay when the controllers are docked in the sides of the Switch in handheld mode.

But since I prefer to play Zelda on my big-screen TV, it was happening all the time -- and driving me nuts. I finally cracked and called Nintendo on a Saturday evening, fully expecting an answering machine to tell me to call back Monday between 10 and 4.

So imagine my surprise when -- again, at 6:00 p.m. PT on a Saturday -- a customer support rep immediately picked up the phone! She spent only a few minutes verifying that yes, I did indeed have wireless issues (and not merely some gunk caught in the gap around the analog stick) and verifying my serial numbers before agreeing to repair my controller for free.

And when I balked at her quote of a two-week turnaround time (that's a long time without Zelda!), she immediately offered to check with a supervisor, who OK'd overnight shipping for my Joy-Con repair. Nintendo even sent me a free shipping label.

Last Wednesday, I shipped my Joy-Con to Nintendo. On Friday morning, I got an email confirming they'd received the shipment, and another on Friday afternoon to let me know the Joy-Con was on its way. This Monday, my original Joy-Con was back (same serial number, same internals) and working perfectly.

What I can't tell you: why this issue is occurring in the first place. One YouTuber suspected Nintendo failed to add a dedicated Bluetooth antenna to the left Joy-Con, and had some success adding his own -- but when I cracked open my own working and faulty controllers, there was no additional antenna to be found.

Enlarge Image Sean Hollister/CNET

But because I photographed the inside of my faulty Joy-Con before I sent it in for repair, we can see the obvious change Nintendo made. They actually added one tiny little thing to my Joy-Con while repairing it.

Do you see it, in the image below? Hint: It's not a new board, a new chip or a new wire.

Enlarge Image Sean Hollister/CNET

Yep! It's that little black square of foam in the lower-right corner.

I spoke to Bill Detwiler, managing editor (and teardown guru) for our sister site TechRepublic, and he explained that it's likely a piece of conductive foam, which is foam that's been specially treated with nickel, copper or both so it can shield electronics from RF interference. (It's often used in portable electronics when there isn't space for a traditional shield.)

Unless we're totally mistaken, this piece of foam is sitting directly on top of the Joy-Con's antenna traces, too, which suggests that it's protecting the antenna from interference.

(Another possibility: the foam may be keeping the ribbon cables for the joystick and/or trigger button, which run through that space, from touching the antenna.)

I even tried removing the foam, and sure enough: The controller stops working properly when it's not there. Seems like an open-and-shut case.

Has Nintendo fixed the problem at the source?

Enlarge Image Sean Hollister/CNET

There's one more interesting wrinkle to the story. In addition to calling customer service, I bought a brand-new $50 controller on Amazon. (I blame free one-day Amazon Prime shipping for my weakness.) While it was ultimately unnecessary, it provided me with an interesting "control" comparison.

Because, out of the box, the new Amazon-bought Joy-Con seemed to work perfectly, too.

Even weirder: Cracking it open revealed that the working controller from Amazon doesn't have the foam. And while it doesn't otherwise look any different to my eyes, it does have different codes on the top center of the circuit board ("0-4" and "16342" compared with "Q-1" and "16402" on my original controller).

Enlarge Image Sean Hollister/CNET

This is speculation, but maybe Nintendo has already modified its manufacturing process, and that the differently labeled Joy-Cons -- the Amazon batch -- rolling off the assembly line don't have the desync issue.

But again, that's merely a theory; Nintendo doesn't seem to want to confirm anything. This is all that Nintendo was willing to say at the time of this writing:

At Nintendo, we take great pride in creating quality products and we want our consumers to have a positive experience. It is common with any new innovative consumer technology for consumers to have questions, and Nintendo Switch is no exception. There are no widespread technical problems, and all issues are being handled promptly, including the reports regarding the left Joy-Con Bluetooth connection. To best support our customers, we continuously update the online consumer support site and provide real-time answers to the questions we are receiving. We want our consumers to get up and running quickly to have fun with Nintendo Switch, and if anything falls short of this goal we encourage them to contact Nintendo's Consumer Service team. For help with any hardware or software questions, please visit: http://support.nintendo.com.

Nintendo also told BGR: "The total number of repair or replacement requests for Nintendo Switch, including for Joy-Con, is consistent with what we've seen for any new hardware Nintendo has launched."

Hopefully Nintendo will give us a more substantial explanation soon. In the meantime, don't hesitate to call customer support. That's 1 (800) 255-3700 in the US, +44 (0)345 60 50 247 in the UK, or 0800 743 056 in Australia.

If my experience is any indication, they've got your back.

Update, March 22 at 11:25a.m. PT:

Nintendo says the left Joy-Con's wireless issue was a "manufacturing variance" that affected a small number of units, and has been fixed at the factory so that future batches shouldn't have the issue.

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