Mine's also warped... a couple weeks ago was ok, i've been playing it 99% of the time docked.
Yesterday i pulled it out (Nintendo came to collect the joycons to repair the disconnect issues with both), left it in sleep mode on top of the bed for a couple hours, when i went to put it into the dock, it wouldn't slide in as usual, i had to force it down for it to sit.
I pulled it out and that's when i saw it, the back is arching outward, mainly the bottom part... sob! Now it wobbles when flat on the table...
I can only guess it's from the heat it generates, my dock is not warped... looks like i gonna have to call nintendo again!
If this is a recurring issue, i can see myself getting a new switch from nintendo every 2 months or so... and the summer heat din even start full strength here.