Screen into another Mac
Full macOS screen sharing over the private connection. Apple’s own, so it behaves exactly as you expect.
After a wake
It will show its lock screen until someone signs in. Nothing has gone wrong — a lock screen after a wake is the expected outcome, not a failure.
Policy block
If a rule forbids Screen Sharing, Rig says so in words and names the rule. This is a policy block, not a network problem.