Fix Acrobat XI Form Script Error

I'm experiencing an error with Adobe Acrobat XI that occurs while opening the pdf. When someone opens the document, the fillable forms (which should be blank) are full of strange symbols (see attached screen shots).

Not sure if it's relevant, but the document is first uploaded to, then downloaded from an online platform called Digify.

Key Requirements:
- Diagnose the cause of the issue

Ideal Skills:
- Expertise in Adobe Acrobat scripting
- Experience with Acrobat XI forms and troubleshooting

Looking for a freelancer who can quickly identify the cause of this issue.