Actually, "Don't Sink" GPWS caution sound is only supposed to happen in an altitude loss after takeoff or during a missed approach.  

If you're descending, and then begin climbing, it's likely that GPWS believes you are going missed, in which case until you're off the GS and intercept it again, it should then begin the warning if you have a negative climb (descent).  It should not trigger outside those conditions, and a correct approach GPWS would be the "SINK RATE! (WOOP WOOP) PULL UP!" if you were sinking too fast.

I get it (constantly) during auto land, even when I've set up properly and have no condition which should trigger "DON'T SINK!"