Video showing bug:
https://www.youtube.com/watch?v=hl9Oao6qKo4&feature=youtu.be
So I don't know how to reproduce this.
I pressed escape, clearly, but then when I was in the menu, I could still move around, build, mine ore, type in chat, swing my blade etc.
Basically, I could do anything I could normally do when the menu isn't open.
However, I was unable to close the menu, forcing me to alt-f4 out of the game.
Later on, the audio glitched out too, seemingly only playing sound-effect clips such as the water, parts of building a new structure ( other parts of that audio of placing a foundation were gone)
Leading to some weird clicking sounds.
I was in the crater in the northern forest where I had heard spiders(?) before underground, but with this audio-glitch, that sound was VERY loud.
This can also be heard near the end of the video.
This happened in multiplayer but I doubt it has anything to do with the cause.