The stock BBM is the BBM version that is installed automatically with your level of OS. So, unless you installed a leaked OS or something then you already have a stock BBM version installed.
I would do the battery pull and try to reinstall through steps 2 - 4 and see what happens.
I followed every single step but still got a failes download with a 907 invalid COD. This is what I did
1. Reinstall stock BBM 188.8.131.52
3.Blackberry ID installation
5. Try to download the BBM v6 but got the same error