What it means is your trying to save a DUF format preset with a Poser figure, your better off either saving the character as a DUF scene or using the old DSA preset format (File > Save as > Depreciated).
While you can convert a Poser figure to TriAx it’s not advisable, they don’t bend any better (in some cases worse), you need to inject all of the morphs into it before hand, because once it’s converted and saved as a figure INJections no longer work, all of your clothing/hair will have to be converted and without support files autofit or TU will use the crappy WM in the figure, all in all a hell of a lot of work.