Hello, My name is ***** ***** I'll be assisting you. I'm sorry you're having problems. The flickering occurring on the bottom portion of the screen is caused by failing LED's inside of the screen/panel itself- which is the most common failure in LED sets out there. This is caused by cheap lighting being installed in the screen at the factory.
Generally, this requires replacement of the LED light strips in the screen itself- which is not something most repair shops will tackle (they will deem the screen defective, which costs 90% of what the TV cost when new to replace- and is not worthwhile).
The only thing you can try on a user level, is to unplug the set from power, then press and hold the power button on the lower rear corner of the set for 20 full seconds, release, then after a minute, plug the set back in and power it up. This drains all residual current from the power supply board and in some cases can enact a reset.
If the issue goes beyond that however, then it is directly related to the panel, and is not a cost effective repair unless you are looking to disassemble the screen yourself and replace the LED strips unfortunately.
Other than that, I'm sorry for the bad news and wish there were a quick fix.
If you need further assistance let me know. Also, please do click a 3-5 STAR rating for my efforts before you go. That is how I am credited for my efforts by the site. You can follow up any time as needed at no additional cost.