Well with some spam clicking around you can walk trough corner of a wall with quite an ease..
Then we figured it's all of the walls that are not connected with corners..
https://gyazo.com/81a11714a98b283ec1bfcf61fd888720
https://gyazo.com/82475be7b785b43841c9e4405a67cbe2
https://gyazo.com/1a0f0cfe62c6eec1214d606293acac3d
https://gyazo.com/923a034d8fe671081354538735a498c9
https://gyazo.com/346e1ab3227e404fb8979ff3fe1bf85e
https://gyazo.com/149affeaab1c6ede16b8a999abcd4cea
Thanks for the bats btw. Took me two characters before we could even reach this place.