Mini wildcat sputtering

Another newbie question---

My mini wildcat sputters when in the water. By that I mean the engine seems to cut in and out even though the remote trigger is held firmly in full speed position. It doesn't maintain its speed longer than a few seconds or a minute or so. When I try it out of the water (although not for as long as I don't want the engines to overheat, the engines work just fine. So it seems to me that there is something loose and bouncing over the waves jars it. The boat is only a month or so old, and we have only used it half a dozen times.

Is there anything that is easy to test or fix? Or should I just return it to the store and get a new one?

If there is any more information needed, I will do my best to supply it.

TIA

David