How this happened: I was playing on a local server on 1.19-rc1, I didn't see other soft locks in 1.19 when I searched the bugs so I'm guessing it's probably in the others too if not fixed. I had my inventory open, and the game window was covering the right half of my screen so I could have reference other things like the wiki and some screenshots of a build I was making. I started opening, moving around, and closing other windows and folders. This included google chrome and the windows photo app viewing the screenshot folder.

When I clicked back on Minecraft, The game was not responding to any of my mouse or keyboard inputs (wasdqe Esc). The window itself was responding, because the text in the title would still fade and bold when I clicked on the window or away from it. I didn't get the "Java/Minecraft is not responding" notification from Windows, and I could see animations in the game still playing. (ie: the game had soft locked). So I closed the window via X button. 

Things get weirder and more problematic. I open the launcher and click play. The launcher warns me that another instance of the game is running and that I am in another world. I check task manager and see that the only related foreground process open is the Minecraft launcher. So I close it. Then I check on the server logs, running on a different system (custom desktop, Windows 10 v. 21H1, AMD FX(tm)-6300 Six-Core Processor 3.50Ghz, 16.0GB RAM) and notice there was no message saying I disconnected, and that I was still in the game. So I kicked myself out of it. The server acknowledges I was kicked. I reopen launcher on my laptop and get the same warning, and close it. In task manager, I search the background processes for anything with "minecraft" in it, and find 5 bg processes labelled "Minecraft Launcher" and I close them. There are no foreground or background processes with minecraft in their name. I open the launcher and launch the game (1.19-rc1) like normal with no warnings. After getting to the title screen, I open this site and start writing the bug report. Then I clearly hear two instances of the music playing and clashing with each other. So I close the game, which kills one of the two tracks. I check task manager, and no fg/bg "minecraft" processes. And as I write this report, I can hear various minecraft tracks periodically play from my computer. I didn't close any processes that were labelled any variation of "java", so it's probably running from that. I'm going to restart my laptop so that it hopefully clears up any lingering processes.