U2715H, banding, but only with moving objects

Hello!

I have an issue with my U2715H monitor that I have tested in a few different ways, and I get the same result with two different computers, different cables and different ports on the monitor. My issue is as followers: When an object with a fine gradient (or a color transition, as in a video or game) moves across the screen, the object (while moving) displays banding. When it is still, there is no banding and the gradient appears fine. An example is the gradient bar in this link. When the window is still, the gradient is fine, as well as when moving it vertically. But when moving it from side to side, the gradient does not remain smooth, but instead looks like a very low color bit-depth banded gradient.

I've tried this on my pc running Windows 7 and a AMD Radeon HD 6870 with the latest drivers (connected with DisplayPort, and also tested with HDMI), as well as from my iMac 2013 (connected with DisplayPort). With my iMac I have both screens up, and I can have the gradient on my iMac screen, wiggle it around with no banding whatsoever, move it to my Dell screen, wiggle it, and immediately the banding is apparent. An important note is that this problem is made significantly worse by setting my monitor's response time to FAST instead of NORMAL. Having it on normal makes it better, which is weird since a faster response time should give me smoother and faster color transitions, with less banding, not the other way around. Another thing that makes this issue a little better is (as described by user tenderchkn in this post by lowering the bpc from 8 to 6 in my AMD Catalyst Control Panel. Again this is very strange, since a lower color bit depth should result in more banding, not the other way around. What is going on? Why am I getting banding when gradient objects or moving color transitions are appearing on my screen? Here is another user who seems to be having the same problem at 0:35 you can clearly see the vertical lines. Something tells me this is not a defective monitor issue, since several users appear to have similar problems.

Would be thrilled to hear if someone else with the same monitor can drag the gradient bar from quickly from left to right and NOT get this issue. That would indicate that this is a defective monitor issue. Thankful for any help I can get!