Quick answer: Unreal Iris snapshot recap skipping dormant actors that should be visible to late joiners? Dormant actors must flush dormancy explicitly before snapshot - mark dirty before recap.
Late join: doors that haven't been interacted with since spawn don't appear on the client.
Force flush on snapshot
Server-side: before sending late-join snapshot, mark all relevant dormant actors as DormancyState_Awake briefly.
Or never dormant
For visible static actors (doors, switches), don't use dormancy. The optimization isn't worth the bug.
Audit dormancy use
Default dormancy = wrong for many actor types. Audit; explicitly mark each actor as 'dormant' only when appropriate.
“Dormancy is a CPU optimization. Iris needs it correctly configured.”
If you use dormancy, document the policy per actor type. Implicit dormancy is the bug source.