The headphone plug falls out of the headphone jack.
The headphone plug cannot be fully inserted.
What to do:
Check the jack to see if there is a foreign object or damage.
Make sure the headphone plug is a standard stereo plug and not damaged.If there is damage to the headphones, they will need to be replaced. Nintendo is unable to provide repair or replacement for a licensed or unlicensed accessory.
If your situation is still not resolved, please contact Nintendo Consumer Support.