Duplicate of BUG-000122258: This is a duplicate of BUG-000122258.
解决办法
This issue seems to be size-dependent and making the chart area bigger resolves the issue. However, it may not be an option if you have limited space in ArcGIS Dashboards especially when there are different other elements present.
To help alleviate the overlapped pie chart labels, adjusting the rotation angle of the chart or apply a negative offset value to the labels helps.