Not sure when as didnt see post but you cant lev up the back anymore when you try lev is droped and you get text something bout anti invasion device or something. Anyhow u cant lev up the back no more so looks like the long way around .
You may notice on the zeka tower in the back there is a ramp that goes up from the 1st layer to the 2nd that kinda does a switch back thing. Levitate with invis up the back of it. Be about midway on the up ramp with your group. Kill the spider walker and clear into the 2nd layer. He spawns in that 2nd layer room.