For some reason when i get vectors to intercept the localizor and when i intercept it and click approach hold it stays locked for  most of the final but always turns off when i still have a way to go.. is that normal. Most of the other planes i've flown I've turned auto throttle off pretty far out so i can get my speed right but leave appr hold on till i'm a couple hundred feet out then disengage and land.. but this one turns off about halfway down final and wont re engage.. is that normal its the pmdg 738

Something's wrong... that isn't normal in the sim... sorry don't have a solution though...