Just submited a bug report along with sample code to reproduce the problem.
Thought I may post here to in case someone has a better work around.
Well spotted, Ken. I have voted to have the bug urgently fixed. My comments were: "Urgent. Limiting the alerts to 10 is a serious limitation. In any case, if you look at the source code in the browser, you will [see] a glaring error being repeated."
Your best bet is either
1) to wait till the folks at Adobe fix the bug, or
2) to use your own chart-generating library to generate the chart.
At the moment, I have reduced the data points to 10, as I am charting 10 months of data instead of 12. Fortunately, the bug does not affect html charts. I have not switch to html charts as it is a global swtich in my code and some of my charts are emailed, which can only be done for type jpg or png.
I had a look at cfchart-html.js but it is optimised for download anyway.
Unfortunately, the bug is still present in CF18 update 11 and Adobe has closed the bug saying it has been fixed.
This issue also exists in ColdFusion 2016. I just encountered it yesterday with a barchart in png format. I am told by our server manager that we have all 2016 patches except the very latest - has this been addressed in the latest patch? It is a serious limition.
With cfchartseries type="bar", in ColdFusion 2016, this occur when a chartseries contains more than 10 data points. Problem occurs with both format="png" and format="jpg". When I try format="html" and the following:
I can reproduce the bug in CF18 with the latest patch, so it is likely that the bug is still there for CF16 with the latest patch.