Szenario:

• phpBB 3.2.0-RC1 with manipulated composer.lock and includes/constants.php
• update fwith autoupdater: 3.2.0-RC1-to-3.2.0-RC2
• update DB and files

The updater works fine and offers a download links to download the conflict files. Before the file checking, i've selected: .zip (as files for download)

The conflict download file has no file extension. After trying .zip, which is wrong, .tar worked fine.

So the file extension is:

• missing
• different to the selection from the user.