They are not being completely honest with you. When they say it senses moisture on these machines, it usually does not mean it senses moisture. (Huh?). Many of these models work on automatic mode this way. The timer stops when the heating element is on and runs when it is off. Since the heating element stays on early in the process when the clothes are wetter, the time moves only a little early on. As the clothes get dryer, the heating element cycles off more, and the timer moves more. So there are no mositure sensors to find.

Now it sounds like your problem is that the venting system is becoming clogged regularly. Be sure and clean out the venting inside the dryer, particularly on the blower. Check to make sure the blower is working correctly and that there are no holes in trhe lint filter.

Good luck