Hi DW,
Greetings from Syncfusion, we have analyzed the reported scenario and we like to explain the behavior of our axis in detail. By default, we will have only x and y axis, if you want an additional axis to represent a different value in any other series, you can create an axis with respect to that particular series. So, if the series is removed the axis with respect to it will also be removed and this is the behavior in our chart.
Having said that, we can work around it by setting the item source of the series to null, instead of removing it from the chart. Based on this we have prepared a simple sample and it can be downloaded from the link below.
Let us know if you need any other clarification.
Thanks,
Michael