I was playing around with the new ADS right click with a BK-133. I pressed ctrl to hold my breath. After all my stamina depleted, I pressed tab to access the inventory. My character kept breathing loudly, and my stamina would not fully recover. It recovers a little, and then loses even more. This seems to occur indefinitely.
Also, whilst trying to replicate this, sometimes my stamina would deplete normally whilst holding breath - allowing me to hold it for a short time... and sometimes it would deplete a little and recover - allowing me to hold it permanently.
Update... after testing this, it seems that just accessing the inventory whilst using right click ADS is enough to trigger the bug.