So, the left Joy-Con desync issue has been highlighted for quite some time now, but this is something I just remembered. Several weeks before the Switch was released, the DualShock 4 controller for my PS4 suddenly started having desync issues where control inputs were either not detected or the joysticks were acting "stuck", just like with the Joy-Con. When I received the Switch, the dock was set up next to the PS4 and the desync issue was reproducible only in that area of the room. If I took the Switch elsewhere (e.g. on a train or another house), the left Joy-Con worked perfectly however I'm not able to take the PS4 elsewhere for testing. Is it possible that both consoles are being affected by the same source of wireless interference? I hadn't added any wireless devices to the room during the time when the DS4 started glitching, but it's possible that a neighbour could have done so on the other side of the wall. If the cause is the same, could a DS4 also be remedied with the same method as the Joy-Con conductive foam trick? Additional note: The control issue with the DualShock 4 is sporadic, however at the same time this started happening the audio output from the controller started skipping constantly and was rendered unusable. Other Bluetooth devices in the room such as dedicated speakers, keyboards, and watches were not affected at all.