Bit late to this thread but I know a few commands that might help if you're stuck:
manage-bde -off C:
(or any other drive)
This decrypts the volume and turns off bitlocker
manage-bde -lock/unlock
manage-bde -protectors -get C:
(or any other drive)
This displays your 48-digit key. I suggest you store it somewhere, just to be safe.
Get-BitlockerVolume
reveals which of your partitions are encrypted with Bitlocker.
Disclaimer: I am not a terminal nerd, I just had similar problems years ago and went down the rabbit hole, used these commands and turned off bitlocker permanently. I don't use windows anymore, but when I did, it didn't cause any problems with bitlocker after this. If you're concerned about your un-encrypted hard drives, consider using Veracrypt (carefully!) or similar open source encryption software.