allowMutatingData property
By default, (because of memory and performance reasons) the chart does not copy the data but keeps it as a reference. In some cases, this might result in mutating the original data source. In order to prevent that, set that property to false. Please note that changing that might decrease performance, especially with bigger sets of data.
API Docs: https://api.highcharts.com/highcharts/chart.allowMutatingData
Implementation
bool? allowMutatingData;