Wordpress form-builder plugins throwing errors

I'm trying to use some Wordpress plugin to make a form with possibility to upload files by users. Every form-building plugin I installed build form correctly but was unable to submit - it throws an error like "ReferenceError: ObjectName is not defined".

FileAway throws: ReferenceError: FileUpConfig is not defined

Wordpress File Upload throws: ReferenceError: wfu_Initialize_Consts is not defined

Huge IT Forms throws: ReferenceError: huge_it_obj is not defined

I can't find any information about this on plugin site or on Stack. Other plugins work well.

Thank you in advance for any help.

via Chebli Mohamed