My step amcharts disappears with too many data points

I'm using amcharts v3 AmGraph to display some changing thresholds across time. Currently using the step type with noStepRisers set to true.

var thresholdGraph = new AmCharts.AmGraph();
thresholdGraph.balloonText = "[[category]] <b><span style='font-size:14px;'>Activity Thresholds: [[Threshold]] L/h</span></b>";
thresholdGraph.gapPeriod = 0;
thresholdGraph.id = "Threshold";
thresholdGraph.lineColor = "#CC0000";
thresholdGraph.markerType = "line";
thresholdGraph.minDistance = 0;
thresholdGraph.noStepRisers = true;
thresholdGraph.stepDirection = "right";
thresholdGraph.title = "Activity Thresholds";
thresholdGraph.type = "step";
thresholdGraph.valueField = "Threshold";
FC_consumption_by_TimeSeries.addGraph(thresholdGraph);

Our data points is every 5 minutes. When we select 1.5 days of data (432 data points), the threshold "disappears" on a 13" monitor [demo 1] (the tooltip still displays), but it displays on a 22.9" monitor [demo 2]. When we select 7 days of data (2016 data points), the threshold does not show on the 22.9" monitor either [demo 3]. But when we zoom using the amcharts function, the threshold reappears [demo 4], but the chart becomes "dashed" because of the noStepRisers?

Also, if noStepRisers is set to false, the threshold always appears with the vertical lines. [demo 5]

I suspect there is a minimum pixel width to the stepRisers which is preventing the steps from showing. The end goal is to have threshold lines always with no "stepRisers".

My 1st post in stackoverflow, please let me know if more details are required. Any ideas/known issues/workarounds/previous discussion links welcome. Please help!