Trader llamas immediately disappear when spawned with a spawn egg

can reproduce

I can confirm this. Similarly, trader llamas created with a summon command despawn instantly

Command used is /summon minecraft:trader_llama ~ ~1 ~ {NoAI:1b,Silent:1b,NoGravity:1b,Variant:3b}

Probably caused by the fix of MC-143699.
The trader llama spawns with a despawn delay of 0, which causes it to instantly despawn.
To work around this, give yourself an egg with a proper delay set:

/give @s minecraft:trader_llama_spawn_egg{EntityTag:{DespawnDelay:3000}}

Note that contrary to the trader llama, the wandering trader doesn't despawn from a spawn egg even if DespawnDelay is 0. But it will normally despawn over time if you set the DespawnDelay manually other than 0.

Also, when breeding two trader llamas, the baby trader llama immediately disappears as well, see MC-151047

Still present in 1.14.2 pre-release 2

yes. in the pre release 2 the spawn egg seems to work but the llamas still disappear when bread.

→ MC-152044

I had never seen this bug until the latest update, which apparently resolved the bug of Baby llamas vanishing after breeding trader llamas.  I can report that they are now vanishing on my Minecraft Realms server when you breed trader llamas, where as previous to this fix, they were not.

→ MC-152044