Of course your satellite signal will be lost whenever the signal from the satellite is blocked from the antenna...that's not poor implementation, that's just physics. Satellite signals obviously aren't like FM or AM bands that transmit from towers...they need direct line of sight with the satellite. I believe some systems get around this by saving several seconds worth of programming, but in the end there will be no programming if you are in a tunnel or parking structure where the antenna is blocked from direct line line of sight with the satellite.

 

Actual line of sight does not appear to be necessary for my car. I still get reception in my parking garage at home. Although the garage is street level and is open, I don't lose the signal in the center of the garage where I am definitely not LOS with the satellite.

 

There are terrestrial repeaters in urban areas to avoid drop-outs from tall buildings, etc. You do need line-of-sight if you're somewhere with no repeaters.