RRZishe it seems like it is a graphene OS issue...
If lots of people running GrapheneOS don't experience the issue (which seems true), and meanwhile some people not running GrapheneOS do experience the issue, what makes it seem like a GrapheneOS issue?
As a random example, perhaps your device's battery is suddenly going bad. That would probably be a battery issue.
It could be a GrapheneOS issue triggered by a particular application mix. Or it could be a problem with one or more apps that would also occur if those apps were run on AOSP or on Google's OS.