Try running the dryer with the vent hose removed. A slow vent will cause what you're describing.

From there you'll need to look at the cycling thermostat. That is the part that tells the timer to advance. It sends a signal to the timer when the proper temp is achieved in the drum. In other words when the element cycles off the timer motor moves a little bit. When it cools down and the element comes back on the timer stops. This action takes place when you're using one of the auto cycles.

If you have a slow vent it can cause the high limit thermostat to do the cycling instead of the proper one.

You can find a parts breakdown and a wiring diagram at the below link.

Model LDE8424ACE