My gut says all of these HUD issues are related to this core issue: Join In Progress needs a 5 second delay for certain devices/events
Workarounds that have been identified typically involve disabling the device on player joined, sleeping, and then re-enabling the device. I believe the reason for this is that the player added event is being fired too early. So internally, the HUD is trying to show before the FortCharacter is fully loaded.
This aligns with the workaround identified for the conversation device. Initiating a Conversation with a Player while they are Jumping Breaks Their Game (Have to Close Client) - #2 by ryan-qa-xbox
If you Sleep for a short time after a player joins in progress, and then initiate the conversation, it will work properly. If you initiate immediately, the conversation will not show. The conversation will be able to be shown after respawning. I imagine this is because conversations are dismissed internally when a player is eliminated.
However, HUD message devices and Stat Creator devices are NOT dismissed on respawn, so they are never able to be shown again.
Hope this helps 