Silverfire, it is possible that you might be going too fast. Have you tried going slower on the longer bits?
I have been going through the program at 4.0 but recently had to up it to 4.1 or 4.2 because I could no longer go that slow.
I know it is super slow but I have been able to keep to the schedule and now feel my body naturally going towards faster pace (slooowly). This seems to line up with what I have read, "time and form first, speed second."