SharePoint List - permission error adding attachments

Hi all,

We're using SharePoint Online. We have a SharePoint List which has a custom permission level applied to allow people to add new list items but not edit them. We're using the SharePoint List for people to lodge requests for help.

The reason we applied custom permissions was to ensure users couldn't edit some of the fields we want list administrators to edit.

However, when people create a new list item and add an attachment, on clicking save they get a permission error:

The list item still creates, just without the attachment.

I've tried hunting for solutions but not coming up with anything. I also read articles on avoiding using attachments with lists however in this circumstance, it's needed at times to support a request from the business and more often than not, attachments aren't being provided yet we want this functionality to work.

Any ideas as to how we can allow end users to create list items and add attachments yet not provide them the ability to edit the item after creation?