Thanks for linking the file. The problem was just that the timestamps in this data are erroneous at the very start... I starts at 905363 ms, then immediately goes backward to 905282, and then goes on to 905353, 905363 (repeated from before), and so on. Backwards or out of order data tends to be problematic, as there's no correct way to process it, and it can lead to some weird behavior. But if I were to guess, I'd expect that this is a rare fluke in the data, so hopefully it wont be something that happens very often with your data system.
In any case, once I deleted the first two data rows, all appears to be well. Here's a link to the fixed version:
https://drive.google.com/file/d/0BxW...ew?usp=sharing