The elements I used adjustments on were in groups, but they were not in sub-groups within the main group. If I understand you correctly, you tried and failed to apply adjustments to subgroups. I wonder if you had opened the sub-group and then tried to apply an adjustment to an element within the sub-group, not the entire sub-group, if that would have worked.
I realize that AP is a pixel based program just as PI was pixel based. Even so, the lines were smooth when drawing a shape, etc. I am going to try it again and if I still get the same results, will report it as a bug.