Graph shows up - missing sections

[pdavis2008]

So the long and short of this issue is that on one of our Cacti instances, we have an issue that is inconsistently occurring for some hosts (not all graphs for each host affected), not all and not at the same time. I've not been able to correlate any network or resource exhaustion events to determine what might be causing the problem. I've included a screenshot of one of the less-affected graphs.

[cigamit]

What does the Cacti log show?