DrawPlus X5: Failing to render most unicode characters

I've written an AutoHotKey script that converts all alphabetic characters to punctuation and mathematical symbols to allow me to keymash filler text with the aim of producing something that looks like a sans serif typeface but isn't readable ... so not Lorem Ipsum and not Greek ... literally.

However when I type or copy and paste unicode characters into DrawPlus X5 it shows most of the characters as boxes (top image) and only renders them correctly while dragging or resizing the text box (lower image)



I've tried different fonts, I've tried various OpenType settings, spacing, kerning on and off, pasting the text in (as unicode).

This is on Windows 7 SP1 64-bit, 8GB RAM