Values drawn after refresh are spaced incorrectly

[jsvd]

Cubism parameters are step(1e4).size(720) and the div element is 720px.
I'm reading from graphite (gauge metrics uploaded by statsd with flushInterval 10 sec).

After refreshing the page, the following redraws are "ugly". Here's an example after a while: http://i.imgur.com/V6D4gtg.png. The difference is very noticeable.

If I refresh the page, the whole horizon is drawn correctly (like the left side of the image).