BUG? Reset to Saved Defaults in Layout Options

In Layout Options, when I select a part and click on “Reset to Saved Defaults”, the Page Margin settings disappear. Selecting another part and then back again restores it.
Screen Shot 7.png

Yes, I know about this. The Layout Options dialog is a slightly fearsome beast and those controls in particular are quite awkward. I daresay this will eventually bother me enough that I will try to fix it, but that day is not likely to come soon.