i think your problem is what i call a "nice rub"!

you can't even hope hitting a wall and go without lose at least 5 shield on it.
experienced it on subsonic/mach1 zones, and even if i hit the wall very smoothly, i mean the ship just give a kiss to it, i grind it all the way and can stop the love only a few seconds later... only 2, and you are good for a perfect zone for nothing...
major problem to get zeus...