I am still having the same problem (not able to edit) the course builder —with or without the use of prerequisites. I tested the course builder by starting from the ground up with a fresh installation, 1 course and a total of 8 lessons —without the use of prerequisites —and the course builder unfortunately broke. I started with 4 lessons, added two, and then two more and kaboom!
So, for my next act, I will attempt the same test, while also disabling all plugins except lifterlms and the following integrations: bbpress, buddy press and lifterlabs. I will let you know what happens.