I've been testing this amazing datapack and playing with the gadgets when turned my gamemode into spectator and then i saw that a lot of villagers were standing in the air. They're not a problem when they're not in front of a crafting table or something because we cannot interact with these.

I think they appears when we hold something from the datapack like the multimeter.
Thank you for your time.

mechanization comes packaged with a older version of DU. which is meant for 1.13 only

Oh I forgot to tell that i'm playing with other datapacks and i think it's the problem because these villagers don't appears when there is only mechanization on the world.

What other datapacks? It's possible they're messing with the villagers in some way that Datapack Utils doesn't expect.
However, this is a tad strange because villagers are bound to a specific player, and if that player deselects an item with click detection, all bound villagers are killed.

The datapacks on my world are:
-Mechanization
-Datapack utilities
-Magic sorting system
-Math lib
-Nitwit trade
-octuple stairs
-rotten to leather
-tree capitator
-all mob heads
-anvil mending
-carpet on stairs
-chestplate + elytra
-d2g elevator
-double shulker shell
-furniture datapack
-item frame color
-soulshard
Yeah that's a lot and i should put less datapacks :/
However i think the problem could come from nitwit trades because the villagers the datapack uses are nitwits, but i'm not sure.