We finally solved our problem with the boosters shutting down and reversers chirping. The problem was the booster and command station were out of phase. To fix it, I swapped the Rail A and Rail B wires on the DB150 booster.
FYI: To check booster and command station phase on a Digitrax system (others might be similar), set a throttle to address 00. With no analog locomotive on the rails (or if you want to test your trackwork at the same time go ahead and leave it on) set the speed to 99. The Track Status LEDs should be all RED or all GREEN and not orange or a combination thereof.
Thanks to everyone who offered suggestions.