Having this issue as well. It's gone completely bonkers. I do not recall having this issue on DP6 and I know I didn't for sure on DP5, but it's here on PB2.
I should note this only happens with my HDD but I keep a USB mini device plugged in 24/7 and the storage is reading correctly with that device.
I tried reindexing my hard drive in spotlight and it fixed it for a few minutes but then it went all weird again. Hopefully they are aware of this bug!