I recently discovered an issue with my own addon (Dr > Breen's Private Reserve Weaponry). Select weapons suddenly failed to play their deploy and reloading sounds.
This persisted through a validation, full reinstallation, addon purge (minus this one), and deletion of the sound manifest script.
The sounds in question are ones that are tied into the weapons' models / QC files.
However, as a last resort I switched to the normal branch of the game and this corrected the issue.
Has this occurred to anyone else?