Also experincing this error. I'm using Windows 11 and my son uses Windows 10. We're on the same LAN. The world we play in is hosted on my computer.
This issue started after we received the 1.19.62 update. Sometimes if my son retries joining the game it works after the 5th or 7th retry. Other times it hangs trying to join the multiplayer game without showing the "P2P/SIG" error.
The problem is completely gone, thanks. The only drawback was that in the last world I was trying to play with my son, when we received the fix, made me lose my inventory, but no big issues.
Now the multiplayer join process is very fast. Thanks a lot!