file_get_contents error for upload fields

[green17]

What happened?

We recently upgraded from Freeform 3 to 4, along with upgrading Craft CMS from version 3 to 4. Our setup includes several file systems configured without public URLs for security reasons. When using the upload field with a standard, publicly accessible file system, everything functions as expected. However, when we use a file system without a public URL, the form fails to submit and generates an error - file_get_contents(test/file.pdf): Failed to open stream: No such file or directory.

Although the file is successfully uploaded to the correct location, the form will not submit.

Errors and Stack Trace (if available)

No response

How can we reproduce this?

1. In Craft's filesystem settings, toggle the "Files in this filesystem have public URLs" to off for a filesystem.
2. In the form builder, choose this filesystem as the asset source for a file upload field.
3. When the form has loaded on the front end, choose a file to upload and submit the form.

Freeform Edition

Pro

Freeform Version

4.1.23

Craft Version

Craft Pro 4.13.5

When did this issue start?

After upgrading from older Freeform version

Previous Freeform Version

3.x