In my FrameXML\DurabilityFrame.xml the parent is UIParent.
https://github.com/Ketho/wow-ui-sour...tyFrame.xml#L4
Have you tried:
Lua Code:
DurabilityFrame.ignoreFramePositionManager = true
In the XML at the bottom the frame position manager is called "OnShow". Setting the ignore value may help.
Additionally enabling SetUserPlaced(true), SetMovable(true) can help sometimes too.