Finding that grouping items and then applying an effect (like outerglow) to the group causes transparency issues when printed. I have a graphic created with multiple paths, grouped it, applied outer glow, and now when printing, the overlay "box" of the grouped item interacts incorrectly with the layers below it when printed.

In the attached image:
1. Design without grouped elements - the white burst in the background looks fine
2. Design with the grouped elements with effect applied, notice how the "box" around the mask is sort of visible? Like there is an effect on the box causing it to interact with the white burst oddly
3. I outlined the border so you can see it

The box around the grouped objects also is not the same as the actual boundaries of the grouped object .... like InDesign flattened it and created a custom outline tight against the outer edges of the paths.

Once I ungrouped the items it asked to delete the effect and I did. Reprinted and it came out fine. Hope this makes sense.