When in TV mode or Tabletop mode (without joycon attacched) switching to Portable Mode (WITH joycon attacched), a crash occurs wich says "Software was closed due to an error" (or something, in italian "Il software è stato chiuso a causa di un errore").
Steps to reproduce:
1) Tabletop mode: play locally with two player split-screen (I have played with a joycon pair and a pro controller both official)
2) Connect another pair of joycon attaching those to the console. (To play 3 players split-screen) The error can occur even now.
3) Detach the joycons... the error occurs
Similar steps but in TV Mode:
1) Start the game in TV Mode: two players are playing splitscreen (joycon pair 1 and pro controller).
2) A joycon pair 2 is attacched to the switch console.
3) Going into Portable Mode raises the error again.
Even with only 2 players:
1) Start the game in tabletop mode / TV MODE: play in a world alone with joycons.
2) Add a second player (Pro controller / other joycons)
3) Attach one of the joycon of player 1 (and go to portable mode) ... error.
The game should do a synchronization with controllers with the current number of players instead of crashing.