TrapDoor open up for too many carts on multitrack stations

On minecraft_server.1.9.jar
I tried to build a station with 4 tracks and a minecart trapDoor feeder for each track.
The first feeder I build is working fine, however when I then make the next cart feeder, all the cart's stored in the feeder is released by a single pulse to the trapdoor. Likewise with feeder no 3 and 4. Only the first feeder build are releasing one cart. Feeder no 2, 3 and 4 build are releasing all the cart's stored in the feeder.