DiaboloVanpire Okay. I was under the impression that this was fixed for most people so maybe some bugs remain.
Also, to make sure this part is clear, the battery stats page that you see there is, as far as I know, pure AOSP stuff. I don't think the GrapheneOS developers have made any changes to anything related to that, so if it's not working it's likely because of an upstream bug. So, for now, if it's bothering you, you can try restarting to see if it starts working again, but over time it will hopefully be fixed by the Android developers upstream.