Reports have been releasing from press outlets that the Switch is having an issue maintaining a sync with the Left Joy Con controller. This is an issue that varies from person to person, but GameXplain looked into the issue. There finds can be found in the above video but what they discovered is that if you cover the Joy Con completely, it negates some of the Bluetooth Signal being sent to the Switch Unit.
This results in unresponsive controls and depending on how bad the situation is, it can drastically effect gameplay. If you are playing the Switch in portable mode with the Joy Cons locked into the system or if you are close to the console, these issues shouldn’t be present much. But it’s good seeing this be tested, as hopefully a more solid fix can be found or patched into the OS of the Switch at launch.