Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: Why does the screen flicker occasionally?
Document: If your a gamer. Than this is it for you! The picture is amazing. Bright and Vivid (I actually had to turn the brightness down. I have a Sony Active 3d Television and I like the 3d Passive. The Passive 3d has no flicker and is very smooth in motion. Trust me folks, I love a great picture for games and movies and this tv does the job. I have not used the SMART TV options yet.
Pictures pop out straight out of the box (watched Avatar and sample videos from Sony Entertainment streaming services). I previously watched 3D at Best Buy on a Samsung, LG and Panasonic and I was never impressed this much. No flicker or crosstalk and I even set the 3D depth to high and no issues. Plus Polarized glasses - no battery.- Motionflow XR 240 does work great.
I recently went through the process of ordering a Samsung PN64F8500 from Amazon. Unfortunately I confirmed that I am one of the few people that are sensitive to plasma trails and flicker. The TV was perfect, great picture but I just could not watch it. More than 30 minutes of viewing any content and headaches etc started. I already knew I had issues with DLP tech but was hoping that the newer Plasma would work. Back to Amazon it went.
The HD images look outstanding and Blu-Ray even better. Even non-HD programming is improved and looks great. I could not detect any ghosting and no speed or motion issues at all while watching a football game in HD. No pixeling at all, ever. I did notice a "Soap Opera Effect" occasionally with some of my HD programming but I noticed that it comes and goes depending on the programming, I guess.
If you're planning to use this TV solely as an HD / 3D display, you'll be OK. Picture is fine, not without flaws. We've had an issue with flickering (poorly designed energy saver? ), and the video occasionally stutters a bit (processor limitations with MotionFlow? ), but it's passable for things like watching from the cable box.The smart features of the TV, however, are horrifically, facepalm-inducingly poor. The TV is very limited in what video and audio formats it can play.
this is the presentation screen for our board room now. it is bright and clear, and works with windows 7 just great.
Very good image and sound. There is light leakage for black screen, which I don't care much but you might.
Played great and 3D was awesome, but after 2 weeks  a black line appeared down the center of the screen. Amazon quickly replaced, but worried it will happen again.
Shipment was fast and in arrived in great shape. Very easy to use and picture quality is superb. Passive 3D is so cool in this unit at 70 inch screen size.
The tv met my expectations in all respects. Picture quality is good, but not as bright and sharp as some other brands, notably samsung. This was expected as I wanted a matt screen because of the bright room in which it is located.
Answer: Could be a couple reasons, would need more info from you. Is this TV at the store or at your house? What is the video feed that it's hooked up to? For all my tech questions I go to AVSFourm.com they're more than happy to answer any question you have and will give you the right techial answer. Hope that helps