In 5.10 (sorry I don't think I'll have time to sort out the AUR package for 5.11 till the weekend), the fill generated by plfill is corrupted if:
1) plsori or plsdidev has been called; and
2) There are a lot of points in the polygon (the threshold is somewhere between 150 and 300).
The issue occurs with a range of drivers (I've tried several in the cairo and qt series and all are affected).
The attached Fortran program illustrates the problem.
Also attached a sample corrupted pdf file. (Can't see a way to add 2 attachments in the original posting)
I believe I have confirmed this issue. See further discussion on plplot-devel