At this time, it is an expected behavior. 4.x labeling engine checks if labels are on exact same spots and keeps one for performance reasons. This behavior is on our radar and we will be enhancing the labels engine to count for scenarios like this one.
I added your information to our issue system.
Okay could you offer an alternative solution?
I am thinking maybe adding another layer with no fill and controlling the labels there?
GIS Analyst – System Mapping
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You are absolutely on the right track for the workaround. I would do exactly what you suggested. I am thinking maybe adding another layer with no fill and controlling the labels there?
As for your second comment, do you mean to filter the layers? As for the layer, you can definitely use the filter and effect. It won't work for the labeling because the labeling optimization happens before filtering.
Please let me know if you need more info.
Hope this makes sense,