[Observium] NaN on Graphs

Hi,

I've been trying to get my graphs to work but I'm still getting NaN on 'some' of my them. I have a Cisco c891fw router and interfaces g2 and g3 graph fine but the other interfaces g0, g3, g4, g5 do not graph and I get a NaN but keep in mind that I do see their traffic transfer rates. I do not get a 'draw error', just a blank graph. I'm running the following:

Ubuntu 15.10

Observium CD 0.15.6.6430

NET-SNMP version: 5.7.3

RRDtool 1.4.3

I have updated to the latest RRDtool version 1.5.5 but then I get the draw errors. Is there anything you can provide to help.

Thanks,

ejw