Code was fine but now error on live site

Hi all! I have a user submission page which allows users to upload 5 images (I have 5 separate upload buttons) All was working fine for a week of being live but now the first image upload button (image1) is failing to upload first time, if the user re-selects image1 it uploads. The code for a 5 image upload buttons is the same except for the field name where it’s being saved to in my collection. I’m quite new to code, I just can’t see why it’s just started to error.