Advanced Content + GBFilePicker not working w/ multi inputs

[tbf]

When adding an input field to advanced content multi inputs of typ 'GBFilePicker', the result is a WYSIWYG box instead of a file picker.

example of input field:

{content_module block='background' module='GBFilePicker' mode='browser' label='Select Background image'}

If this same content module block is used anywhere else (such as in a template), it works fine.

Thoughts?

EDIT:
AdvancedContent 0.9.4.3
GBFilePicker 1.3.3
CMSMS 1.11.10