Here are your parts
Replacement parts for LG DLE5977W Dryer | AppliancePartsPros.com

Here is a service manual
DLE5977xx LG Electric Dryer Repair Service Manual - ApplianceDigest.com
You have to join the site to download the manual but it is free and this is a very good site for manuals and other info for the appliance repair DIYer.

The most common cause of having to run two cycles is a vent problem.

Unplug the unit and disconnect it from the vent system.
Now try a run.
If it now dries OK odds are the vent system needs checking/cleaning.
Be sure to check that the louvers on the outside of the house open correctly.

If you do not want any lint in the house.
Take a pair of pantyhose.
Put one leg into the other and then attach this to the dryer's vent.
Leave enough room so the pantyhose can balloon out like a windsock.

Both the above will let you check the temperature and the air flow.

Note: The above is not recommended for gas dryers due to carbon monoxide concerns.

Strange that it needs two cycles in an auto mode as the moisture sensor on most units will not let the timer advance to off until the clothes are dry, perhaps LG does it differently.

Since the unit looks like a dual element, I would check the heater.
Next would be the thermistor.