Thanks for taking a look.
Unity version: 4.3.2f1
tk2d: 2.3.3
platform: Windows 8
DirectX: 9 (I presume, dx11 check box is not enabled)
graphics card: Nvidia GT 740M
I've attached a different variation of the bug example. I've now changed the update functions to simply slowly scroll along the x-axis. Reason being that a strange thing happened: the camera position I had in the previous project didn't show the bug after I performed a build.
However I found the same problem was now at 51.85 (instead of 51.75). Weird.
Basically, press play and watch the camera slowly pan in the game view. Sorry, know it's boring, but within the space of a minute or two you will see a flicker of one of these gaps as it scrolls over the problem coordinate, wherever that may be (this is how I always notice it when I'm test playing my game).
Just to add more weight to the problem, I have deployed this scrolling example to my Nexus 7 and Nexus 5, and both will show the bug occurring at some point.
I think some kind of rounding problem is still the suspect, but no idea how this might be fixed
* edit * yep, just tested it on my nexus 7 again. Ater about 35s of scrolling I see one, and then there's another 3 or 4 occurrences over the next 20 seconds of scrolling or so.