If the player is not looking at the NPC and that player opens up the NPC's dialogue via the /dialogue command, the NPC's arms will get disconnected in the dialogue GUI.

Steps to Reproduce:
1. Summon/spawn in an NPC
2. Add a tag to the NPC using the command '/tag @e[type=npc] add test'
3. Look away from the NPC
4. In survival mode (courtesy of MCPE-152291), open the NPC's dialogue using the command '/dialogue open @e[tag=test] @s'

Expected Results
The dialogue opens and renders the NPC as is.

Observed Results:
The NPC in its dialogue menu has its arms disconnected.

Additional Notes:
This bug exists due to the fact that mob animations stop playing when you look away from that mob.