I have the same except that my turn off near 52%. After first turn off the phone do the same at every next 5%(47%, 42%, ....).
What date you have on the battery?
I have two batteries:
1. 10W37 (withstands up to 41%)
2. 10W29 (withstands up to 52%)
I think it is obviously the battery fault. That is its use and had to buy a new one. I`m waiting now for the package. The battery with date 11W09. I will check for new one and I will know you if everything ok.
Subscribe please if someone had a similar problem with BST-41 10Wxx series.
I'm not a idiot I do this a lot of time. I'm use for that xrecovery and BatteryCalibration app. I have two batteries with the same problem(I wrote it above). I check this on stock and custom rom. On locked and unlocked bootloader. With sdcard and with no sdcard something else??