When I board the aircraft, the pilots enter the bridge and then cross into the jetway. I can see them the whole time. When the cabin crew boards, I can see them cross the bridge, but they never reappear in the jetway. The 3 cabincrewX_bridge pictures show the first 3 cabin crew members crossing the bridge, but I never see them reappear in the jetway after they enter the connection point. When passengers board, they are visible the entire time. The problem only occurs with the cabin crew.
Shown is gate 76 @ KBOS. I've observed this at KBWI gate A2, and also at (Taxi2Gate) KMCO gate 42.