Sorry my bad, I found the source of the problem:
On DGAppendDialogItem() for Popup-Ctrl:
Before (AC 21 and below) ->
itemSubType
= NULL (no errors, no problem)
Current (AC 22) -> I tried filling up
itemSubType
with an appropriate height (right now the Y size of Popup-Ctrl)
It now works and no longer disappear when resizing.