This is about HeliHUD, but may be it's also related to HID Macros. I've tried HeliHUD with X-Plane 10.30 and found out that it not correct draws font. Look, this is screen before HeliHUD activated:

And this is after:

I know (I tried this) simple:
float rgb[] = { 1.0, 1.0, 1.0 };
XPLMDrawString(rgb, x, y, const_cast<char *> (str.c_str()), NULL, xplmFont_Basic);
works without problem (xplmFont_Basic is defined in the XPLMGraphics.h). May be you'll kindly fix this?
Best regards,
Misha