if you click the screen while the game is frozen like this it will likely crash.

As you can see in this recording, the game runs completely normal and without any pauses, mouse motion is normal, sound is normal, and as expected the clicking a button immediately moves you to that screen.
however, once I open multiplayer screen and then click cancel to go back to the title screen, there is a noticeable delay between when I clicked the button (you can tell when I clicked from the sound effect) to when the game swaps to the title screen.

in the video there is only a short duration of this lag, however my internet is kinda unstable sometimes, I'll try to record it crashing when my internet decides to troll me again.

I'll try to find the logs of when it did crash.
(unfortunately it may not be possible since I recently ran out of disk space and had to clear out a lot of files I don't remember if I deleted those logs, I know I definitely deleted some of the contents of my Minecraft folder so it's not looking like I'm going to find these logs.)

This seems unlikely to be affected my Wynntils. Can you reproduce this without any other mods?

this is with only wynntils

the only thing other than wynntils to replicate this lag is a slow internet connection.