"Failed to Fetch" error with attachments

We have several users who are unable to upload attachments via Plumsail forms.

The "Attachments" field will allow them to select file(s) to upload, but there is no loading animation, and when they attempt to upload, they receive a "Failed to fetch" error both at the top of the form and under the Attachments field. The Attachments field will also be cleared of content due to this error, but the rest of the form remains unchanged.

I've confirmed that the users have Edit permissions to the entire site as well as the list. I am unable to duplicate the issue with my Admin account with "Full Control" over the site.

Dear @pmccarthy,
Can you check browser's console for errors? Also, please, open the Network tab in the browser and try to upload attachment, until you get an error, then export the HAR file for us:
image

You can send it to [email protected], if you don't want to share it here.