Cypher
Very interesting you mention Seedvault backups!
Around the same time my VPN started dropping overnight, I had a notification about Seedvault backups backing up Firefox. This notification was frozen, couldn't be swiped away or expanded in any way. A reboot was the only way to get rid of it. I had to disable Seedvault backups to stop it.
These two issues are the only semi significant issues I've experienced in years of GrapheneOS use, and seems likely they're related somehow. I'll re-enable the Wireguard option on my ProtonVPN app, and see how it fares overnight with Seedvault disabled.
I don't know much about Seedvault, but if it runs overnight that'd explain why people are waking up to disconnected VPNs too.