After updating from 1.9.7(?) Insight graphs have become flakey. Specifically, the history timeline tends to 'stick' on the 2 hour display, and often fails to render the "IN" graph at all.
Note in the attachment pic, that the pie charts and corresponding usage totals are correct for the 30 day period, but the history graph is stuck on 2 hours.
(the pie chart IP address and port details do display correctly, I've simply obscured them for privacy.)