To be honest with you, I'm not sure. Just started working here and they were using U Shaped aperatures on 0603 caps/resistors and getting dry pads. After checking out the programming, no matter how much I slow down the screen printer or what I do, those aperatures get blocked with paste. It's not consistant either. I am ordering a new screen with square aperatures instead of the u shaped ones.
Sounds like someone before you was dealing with tombstoning components. We have had greater success with triangular paeratures for 0603 and 0402 footprints. Granted the pad will not be wetted completly but IPC requirements are maintained.