I am going to take one more stab at this by first presenting the problem as it appears from a flat earth perspective. Please excuse my poor graphics skills, and also I have yet to figure out how to post images inside the message, so both images will appear at the bottom of this message. Click on the thumbnails to make the images larger.
The first image shows the dilemma from a flat earth perspective. The star is the person standing on earth. The moon is overhead and lit from the side. And the two circles on the right side of the rectangle represent the two apparent positions of the sun. The upper circle is where the light striking the moon suggests that the sun would be located. The lower circle roughly suggests where the person on earth sees the sun in the sky. The dilemma is that since there is only one sun, either the moon's illuminated surface is apparently incorrect, or the person on earth's perspective of where the sun is, is incorrect. The flat earth theory thus requires an explanation for this dilemma that involves something like the light being bent by the atmosphere, or perspective changing the location of the sun for the person on earth, but not for the moon's illumination since the sun is supposedly actually located at the upper position in the diagram.
In order for light bending refraction or perspective to make the sun appear lower than it actually is supposed to be in the flat earth model, these effects must be very extreme as there is a large difference between the sun's location as suggested by the illumination of the moon and as suggested by what the person on earth is seeing. If you draw a line between the person on earth and the upper location of the sun and calculate the degrees of the resulting angle, then the sun is appearing several degrees lower in the sky than where it supposedly actually is.
In the round earth model, the situation is suggested to be more like the lower drawing which is not drawn to scale, but will have to do given the limits on image size where you can still see the separate lines of the rectangle. If it was drawn to scale the upper and lower sides of the rectangle would be 400 times as long as the right and left sides. And in order for the sun which is now 400 times as far away from the observer on earth to appear the same size in the sky, it would need to larger as well as depicted in the second diagram. But once you elongate the rectangle connecting the four points in the diagram (observer, moon, upper position and lower positions of the sun), then the observed differences between the sun in the lower position and the sun in the upper position are very slight, probably an angle of much less than one degree from the observer on earth's perspective. The difference in the angle between a line connecting the moon and the sun in the upper position and a line connecting the moon and the sun in the lower position is also much less than one degree. So the difference in how the moon is illuminated would also be so slight as to be imperceptible by the naked eye.
Now obviously, there is only one sun, but the observations are almost identical whether you place the sun in the upper corner or in the lower corner of the rectangle that is 400 times longer than the rectangle in the first diagram, so the video would appear just as it was recorded when using this round earth model, but whether the sun is in the upper corner or the lower corner would be a moot point as the moon would be illuminated from fundamentally the same direction and so the moon would look fundamentally the same to the observer on earth, and the sun would appear in the same position in the sky within a fraction of one degree. And yes, for this model to work, the sun would also be about 4 times larger than the size of the right side of the now 400 times longer rectangle, but because it is so far away, the sun would still appear the same size as the moon. But putting the center point of the much larger sun at either the lower corner or the upper corner of the rectangle would not change the appearance of its location in the sky enough for the naked eye to be able to discriminate that ever so slight change in the angle from horizontal to a tiny fraction of a degree higher than horizontal.
If you step back for a moment, this is the fundamental issue with all depictions of the sun's location in the flat earth model. How is it possible for a sun up in the sky above the earth to appear as if it has set below the surface of the earth? Again, with a flat earth model, you need to have some dramatic light bending or actually impossible perspective effects to make the sun not only appear below the "horizon", but you also need for those effects to be so extreme that during the darkest periods of night all of the light from the sun is refracted away leaving us in the dark. Or the perspective of the sun's movement away must somehow also prevent all light from the sun which is still above the earth from reaching someone on the surface of the earth. It is impossible for perspective to swallow up all of the light, no matter how small the sun would end up appearing, especially at the scale of distance proposed in the flat earth model. The north star is supposedly much further away and yet it does not disappear due to perspective in the flat earth model.
The same dilemma occurs when the sun appears below the clouds as discussed on this thread:
http://forum.tfes.org/index.php?topic=6074.new;topicseen#newIn the flat earth model, the light from the sun which is much higher up in the sky than the clouds has to be bent so that it strikes the clouds from underneath, or so that the shadow cast by Mount Rainier travels upward instead of downward.
The round earth solution to all of these dilemmas is simply explained in the lower diagram as the sun's rays do not need to bend to display the observed effects.
Here are the diagrams. Click on the images to see them enlarged, and note that the lower image appears as a simple line until you enlarge it, so you have to click right on the line itself.