There have been several reports of Switch users having experienced issues with Joy-Con connectivity, most notably with the left Joy Con. The issues have even made some send their systems in to Nintendo for a fix.
As it turns out the process of fixing it is actually rather simple. CNET Australia sent in its left Joy-Con, and received it back about a week later. What did the fix entail? Nintendo apparently just added a black square of foam in the lower-right corner, and this simple fix actually managed to solve the issue.
There is speculation that this piece of foam sits directly on top of the Joy-Con’s antenna traces, suggesting that it protects the antenna from interference. If it is removed, then the issues will resume. As well, CNET has suggested that this is a piece of conductive foam, which isa foam that’s been specially treated with nickel, copper or both so it can shield electronics from RF interference.
In addition to this, CNET has also noted that new Joy Cons are being sent out to retailers, with the problem fixed. Nintendo is clearly on top of things when it comes to fixing problems.