PSA: On the topic of the SwSh Y-COM Glitch (Fixed as of the v1.1.1 update!)

[Max. Optimizer]

There are hacked Pokémon circulating around on Surprise Trade that can cause the Y-COM system to crash games when trying to access online features. (Source)

 

[shiny finder]

"The newest Sword & Shield update (v1.1.1) has fixed the crashing caused by 'maliciously crafted' Pokémon trades. It's fixed!"

As always, be wary of hacks, but the patch has apparently fixed the glitch that bricked your Y-COM if you got traded a malicious mon thru ST.

Source