Highlighting Values don't work for more than 1500 values?

[rskornia]

I have a Scatterchart with two dimensions and two Expressions, that looks like this:

As you can see, the highlighting of values with the same second dimensions works here. The Chart contains 1500 values.

With one value more (1501) the same highlighting doesn't work anymore:

Is it possible to configure the amount of higlighted values?

Is it a restriction due to performance reasons?

In the Chart and Document properties I found no Setting for that.

Thanks,

Rafael