Marker symbols not rendering correctly in PDF

[SeanWray]

I am trying to use a marker symbol. In previous maps it has worked perfectly. Sudenly now it is not exporting correctly. (see attached). No settings have been changed. I'm wondering if anyone else has experienced this and if so is there a fix?

[RyanFanani]

What type of file you're export.?

[SeanWray]

What type of file you're export.?

I am exporting map to a PDF file. I have tried 300 dpi and output image quality set to best.