When closing or opening a door made of any nether wood type, the sound produced is randomly chosen between closing or opening whereas all the other doors make the right sound.
The trapdoors and fence gates make the right sounds.
This can be checked using the command /playsound minecraft:block.nether_wood_door.open ambient @a ~ ~ ~ 255
and /playsound minecraft:block.nether_wood_door.close ambient @a ~ ~ ~ 255
(volume increased since it is originally low)
Can confirm.