Here is a great video from & explaination from ParoXysm QC [x360a - x DIAM0NDZ]. Not mine just passing it along, so all credits go to the author!!.
Chapter 19: Burning Tower
At the very end of the chapter, you'll have to quickly hack two devices to open the giant locked door (LB). You must ABSOLUTELY take advantage of the slow-mo that is provided by the Dart Overlay or you won't be quick enough. Don't worry if you fail, you can simply restart to the last checkpoint.