Neogaf : Multiple reports of joycon issues in switch previews.

[TomaTito]

Faelco said:

Neogaf is now discussing another possible issue with the Joy Cons, experienced by Giantbomb. The Joy Cons apparently come off pretty easily from the tablet in handheld mode, and GB says that it gets easier and easier, apparently possibly to the point where the tablet could fall off while holding it.

"This might be broken by next week"

We'll see if this issue is potentially big or not.

Not sure what he is doing. But if you slot the joycon into the rail, there is a notch that locks it physically.
Only way it would fly away like that was if it didn't reach that notch or if it is broken.

You have to press and hold a release button whenever you want to detach the joycons.