Username: @Jamyn
Within AdGuard Home, the "Phishing URL Blocklist (PhishTank and OpenPhish)" blocks s3.dualstack.us-east-1.amazonaws.com. Steam (a gaming platform) uses the subdomain steamcloud-us-east.s3.dualstack.us-east-1.amazonaws.com to save game state, so blocking this URL means some game saves can "randomly" fail if Steam selects the us-east region for the save. Users will see a generic "cloud sync error" in the Steam client.
Original report: https://github.com/AdguardTeam/AdguardFilters/issues/162573
Can't find a source of the blocking rule.