Other User’s Information Showing Up

Hey there. I have this problem with one website where other users can see past filled-in forms.

So let’s say User A filled in the form and submitted the form. Then User B from a different device and different state, goes to the form to submit something but the form is filled in with User’s A information and if they clear out the details then sometimes the media file attachment from User A also appears.

I have tried applying “watermark” to the input fields and tried resetting the form when submitted. Has there ever happened before? What can I do to fix it?
Thank you!