@jenia,
indexLabels/labels in Pie Chart are skipped whenever they get closer to other indexLabels – this behavior is by design. You can workaround this issue by either rotating the Pie Chart as shown in this JSFiddle or by showing indexLabel outside the Pie Chart as shown in this JSFiddle – indexLabel’s are placed better when they are outside.
It would be useful if you can create a JSFiddle demonstrating the issue with minimal code, so that we can look into your code, understand the scenario better and guide you accordingly.
—
Vishwas R
Team CanvasJS