Upload broke Using DropZone and ASPUpload after upgrading jquery from 2.1.1 to 3.1.1

I have a web application (ASP Classic) which uses DropZone and ASP Persist to upload files.
We were using jquery 2.1.1 and it works fine, but once we upgraded to jquery 3.1.1 we get the error below:

Persits.Upload.1 error '800a003d'

Wrong Content-Type. Make sure you have included the attribute ENCTYPE="multipart/form-data" in your form.

/bluedot_2018/Intranet/Contacts/attachments_add.asp, line 21 

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This is without making any other changes to the code. So evidently Jquery 3.1.1 doesn't support something that it did on version 2.1.1
Any help is greatly appreciated.
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Big MontyWeb Ninja at largeCommented:
do you have the following attribute on your FORM tag?


this ensures data (in this case, file uploads) being sent over is in encoded properly and can be read correctly on the server. If that doesn't work, please post your html / JS code (abbreviated if possible)

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AleksAuthor Commented:
Actually I added that attribute to the form tag and the data from the 'summernote' field was not posted to the Stored Procedure causing an error.
I removed it and now it works again.
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