seems the unbreakable tag for wolf armor makes the wolf impossible to be killed. here its wolf spawn egg with wolf armor with unbreakable tag on the wolf armor:

/give @p wolf_spawn_egg[entity_data=\{id:"minecraft:wolf",body_armor_item:{id:"minecraft:wolf_armor",count:1,components:{"minecraft:unbreakable":{}}}}] 1

wolf can be hurt but don't die even when in lava or fall from high ground. think this its bug.