This bug has been observed and can be reproduced on multi-lingual sites with i18n (internationalization) module installed.

1. Edit a node where the alias had been set manually after unchecking the "Automatic alias" checkbox
2. After saving, the node is forced to have the alias specified in the pathauto settings, even with the "Automatic alias" setting unchecked.
3. Disabling the Path Redirect module restores the correct behaviour.

There is no reason for the Path Redirect module to ignore "Automatic alias" checkbox on a node and force something else.