Some users having trouble submitting form

I have one user who uses one of my forms and every week they are getting an error upon submission. It doesn't appear to be an issue with their internet as the form was submitted from different locations. It also isn't happening for anyone else who uses the form. Could you please advise with any advice to fix this? Thank you.

Hi,

I made a test submission using your jotform http://www.jotformpro.com/form/42304921004945

but so far I could not reproduced the issue.

base on the error screenshot you had provided, it seems the problem is on the file being uploaded. Perhaps you can try testing the file that the user who encountered the issue.

Check the file they were trying to upload if it has any conflict on the required file type by the form.

Hope this help. Please inform us if the issue remains.

Thanks.