It doesn't matter how long away, you are from the source of light, Or Set.
If you're moving just a little, the light on the set will change, Also if your arm is streched, for pressing the 'Picture' button, The light'll change.
Are there any moving stuff, around the set as LEGO Bricks, CD's or Covers?
That's the Greatest way, of getting lightflickers.
Keep everything stable in your Studio, Everything that's moving around the set, will make the light change.
Do you have your curtains rolled up, That will make the light fuss into your room = Lightflicker.
Always were black/Dark cloth, if you're wearing I.E Yellow or white, The light will change, from frame-to-frame.
Do always your Greatest work, if ther' aren't any snow, Snow is reflecting the light, even threw Curtains.
Try to Brickfilm in weekends, You're having better time there, so you can Brickfilm in the darkness, of the night.
Do not have your computer screen to close to the set, That will make the light differ.
Do not turn on/off AnythingWhen you're Brickfilming, That will also make the light differ.
Hope this helps.
-Jack.