Each time I open the game on Switch, I am prompted to link my Microsoft Account by going to aka.ms.... and entering a code as if it is the first time I have opened the game. If I follow the link and enter the code I am able to link my account to the game on Switch and play without issue. But if the game closes, when I open it again, I have to go through the link process again.

This happens if I close the game and reopen it; if I close the game,  the console sleeps, I wake the console, and then open the game; or if the console sleeps, I wake the console, I close the running game (because it does not reconnect to my realm unless i close and reopen it), and then I open the game fresh.

I believe this problem began with the previous hotfix (possibly 1.16.20?). The most recent hotfix (1.16.21) fixed other problems I had been having (game freezing/crashing/causing Switch to freeze), but the prompts to link my Microsoft Account each time I open the game has persisted. 

I did not notice any of these issues (game freezing/causing console to freeze/having to relink my Microsoft account) with the initial Nether update.