Rob,
went out and flew the same ils course. the 3400 showed the green glide slope indicator sitting at the bottom when the 4500 showed it at the top. after intercepting the glide slope and flying almost 2 miles the 3400 glide slope indicator popped up and agreed with the 4500 however the 3400 flight director was reading opposite of the 4500 flight director. Something is definitely not right with the 3400 .
Alan