Thank you for playing and for submitting a bug report! :)
It seems you've hit the boss arena's trigger which forces the character to walk to a pre-determined location for the boss fight. That part is intended, however it should not break when pausing and resuming. I can't reproduce that behavior on my end, unfortunately, but it's in the backlog and I'll keep an eye on it!
When the character is done walking to the arena location, the boss intro plays, during which the cursor is hidden and the camera is static. After the intro finishes, all game controls should return back to normal. Did that happen for you or was it completely borked?