PjMuffin I never had this issue on stock OS so it's some kind of software issue.
Did the issue arise right when GrapheneOS was installed, or after some time?
What release are you running?
If flashing back to Google's OS makes the problem go away, and reinstalling GrapheneOS makes the problem return, that would be an interesting issue to file with GrapheneOS.
But if flashing back to Google's OS does not make the problem go away, then likely it's a hardware problem that manifested after some amount of use.