Thanks for sending the archive. I'm still not sure how your new PDF was different, but I found that there is already a (badly named) .pdf in the C:\Program Files\ptxprint\PDFassets\border-art folder which is 'taller' and designed for Arabic script:
A5 section head border(RTL).pdf - unfortunately, it doesn't work as it is, due to the (parentheses) in the filename (but this will be fixed in the next release of PTXprint).
But, as a workaround, if you change the PDF file name and then use that PDF, it works very well for what you need, and scales without distorting.
So, for example, change the name to be:
A5 section head border-RTL-taller.pdf

Notice that you can also SHIFT the graphic down slightly, and SCALE it to be larger if needed.
And you may want to consider making a small change in size to the \s Style so that the upper and lower diacritics all fit in the space available.

It all fits quite well once you've got the right settings!

It looks like the dynamically-generated Text Border also needs some settings tweaked:

Note that there are Box padding and Border padding settings; and it might help to use negative Box Padding.
