Rimworld freezing - Possible pathing stutter

[thetaprime]

In 1.1 I have noticed when I am mining or placing a block on a mountain map, there is a small stutter after each block is mined or reach block is placed. At first I though a mod was to blame but I have reduced my mods to visual only and the same thing occurs. Not quite being able to figure what was causing it, I continued to play and broke through a wall opening a cave at the back of my base, and all of the lag disappeared. I walled the path to the cave back up and boom, the lag is back. I wonder if this is a base game issue with pathing, but only really shows up when you load the game down with some mods?

EDIT: I have removed all mods and started on the same map in vanilla, and I am getting the same lag on this map until I break through into the cave structures. I wonder if pathing is not ignoring unreachable points on the map?