What is the undergroun bear spawn bug

[Skelegutplays]

So, i have recently been hearing about this ”underground” bear spawn bug somewhere near the unnamed pond in mystery lake. Im going to go there soon and i want to know what it is about where it is and how rare is it.

[ajb1978]

In a nutshell, a bear sometimes spawns below the terrain in Mystery Lake by the Unnamed Pond, close to the rock wall that serves as the western edge of the region.  You can hear him moving around, but you can't see him.  If you hear bear sounds but see no bear, stick near the wall, just north of the ice.  You should be able to follow the sound to where it should be coming from, and if the conditions are right the invisi-bear will see you, and maul you.

Personally I've only noticed it once, but I was just passing through on a moose hunt and didn't stick around.