This has happened twice, once on a 1.19.3 server a while back and just now on our 1.20.1 server. On 1.19.3, the dog was riding in a boat with the player, in 1.20.1 the dog was riding in a Eureka Airship with the player. Both times the dog was riding on another entity.

The server crashed, and when everyone got back the dog was gone. All other entities were accounted for. It seems to exist on the creative radar but when we get to the location it is invisible and undetectable. Whistle doesn't work. Can't respawn it because it is not dead, can't use the conducting bone because it gives an error "ALREADYREQUESTORLOADED". Global kill command doesn't seem to kill it for respawning. The dog is just in limbo as a UID and a name with no entity... and unreachable. On 1.19.3 we gave up and created a new dog. But that dog non entity never left the server. It was always there. Now in the 1.20.1 server we are facing the same choice. By coincidence, both times the dog's name was "Luna". The 1.20.1 "Luna" was a revival of the one that was lost in 1.19.3. It is ironic.

Is there anything else that can be done?

Sorry for the lack of info... I was wondering if there was a command or something that could bring the dog back. The current crash was probably a hanging thread crash. We are having chunk loading issues and sometimes travel will cause chunk loading to hang for longer than the server will allow. It is DTN version 1.17.2. I am attaching two crash reports because I was not on the server at the time and this is the time period it happened. There have only been two incidents of an entity riding with a player vanishing due to a server crash and both times it was the dog. In fact, it happened to the same player with the same dog with the same name...but on a new server in a new version of DTN. It might be a coincidence... but everyone on the first server had DTN dogs. This was the first dog on the new server.

I will do some tests tonight and see if I can repeat it.

crash-2023-11-05_17.03.00-server.txt
crash-2023-11-05_12.52.28-server.txt

Could you please you provide more informations?
Which DTN version are you playing on?
Could you also provide the crash logs at that momment the server crash?
Can you still replicate it?
Ps: There is actually a pretty similar issue #18 which should have been fixed a long ago. But i am not sure if it is related to this. Although one thing i can predict is, if it is a hard crash (by that i mean it have the same effect as force killing the server via task manager, or pulling the plug while the server is running, or an exception which cannot be handled (StackOverflowException)) then every entity who share the same vechicle with the player will be corrupted, because how minecraft save the entity sharing the same vehicle with the player.

Thanks for the insight, will take a look asap.
I mean, usually if the world is properly saved then you can always do /dog revive and /dog locate to get your dog back as long as data integrity is garanteed. Otherwise then it hugely depends. But it seems like to me that the crash have caused data corruption which corrupts the dog itself (entity sharing the same vehicle with the player, every entity not just the dog), if it is the case then there is not much we can do unfortunately.

OK Thanks for the info. We tried to duplicate it today with a new dog on the airship. We got the server to crash from chunk loading but the dog was fine when we came back. Whatever happened must have been a different sort of crash. Or maybe the missing dog's training had something to do with it. She was training the new flight feature which is awesome.

Thanks for the insight, will take a look asap. I mean, usually if the world is properly saved then you can always do /dog revive and /dog locate to get your dog back as long as data integrity is garanteed. Otherwise then it hugely depends. But it seems like to me that the crash have caused data corruption which corrupts the dog itself (entity sharing the same vehicle with the player, every entity not just the dog), if it is the case then there is not much we can do unfortunately.

I have also encountered invisible dog issue when game crashes in single player world.
I use not enough crashes mod so the game won't close just go to the home screen. When I load the world my dog is invisible . When I quit the game completely and opened it again the problem is fixed