Good thought. That can, indeed, cause the problem. There are two ways to tell that I know. One is just by the feel of the recoil. When you have a load too light to cycle the slide 100%, the gun feels spongy in recoil because the slide doesn't slam abruptly to a stop in counter battery. It also tends to be less consistent feeling, because as the stack in the magazine gets shorter, the upward drag decreases and you feel the resulting change in the slide motion.
The second test is related to the fact light loads that barely push the slide back need all the frame support they can get. Shoot your gun from a Weaver stance or by pressing it firmly down into a carpet scrap on a shooting bench. If the problem decreases noticeably with the firmer frame support, the round pressure is your likely culprit.
I don't know if lighter recoil springs are available for the Taurus as they are for 1911's set up to fire lighter loads, but if not, you could buy a spare for full-house loads, then get one lf those cute little 8" compound bolt cutters from Sears and start cutting turns off one end, one coil at a time until it functions.
Also, I don't know if the Taurus uses a recoil buffer of some kind? If so, and it is one of the secondary recoil spring types, then it could be foiling your light loads and should be defeated for shooting them.
Nick