uploadfilecheckoutattribute, Error 404, when trying to upload a file.

This has been potentially broken since I upgraded to 4.0, but its not used very often and I didn't test it.

I have an upload file option on a checkout attribute.  When I click 'Upload a File', I browse and select a valid file.  It fails with an error stating this.  In the console, I have two errors.  One from jquery.fineuploader-4.2.2.min.js, which states am Error when attempting to parse xhr response text (JSON.parse Error: Unexpected input at position:0)  The other is HTTP404: Not found - The server has not found anything matching the requested URI (Uniform Resource Identifier).  (XHR)POST - https://mywebsite.com/en/uploadfilecheckoutattribute/8

I believe the issue is that of the 404.  Checking the code against the source of 4.0.  The ShoppingCartController has an IActionResult of that name as does the source.  I then checked RouteProvider.cs and it has an entry as does the source that looks fine.

I have used fiddler to post to this url and it is indeed returning 404.  I have no idea how to debug this, anyone any ideas?

Steve.

Update, it is being hit.  If I use an attributeID which is incorrect eg one that is not a upload type.  It returns JSON stating a false outcome.  If I pick my valid attribute ID it returns a 404, even though the code doesn't appear to show that as an outcome.

Fixed, I have a plugin which moves files to Azure Blob storage, but it has reverted to file system.  As the VM is not persisted I believe the permissions are locked down therefore the random error.  Moving the setting to Azure and everything working again.

Steve.