My armor stands are invisible in all my worlds. I have no resource packs applied. My global resources are empty except default. 

I have not given the armor stands any effects or tags. Except a nametag.

I have tried placing more armor stands (unedited straight from the creative inventory) and they are invisible. I have tried various orientations. I have tried in multiple worlds. I have tried "/effect @e clear".

Armour, heads, and items appear correctly - they appear to float.

Steps to reproduce (exactly as I did it)

Place an armour stand.
Name it "Vertical with a nametag."
Use command blocks to give it levitation.
Use command blocks to execute teleport commands on behalf of the stand.
Exit the game.
Reload the game.
All armor stands have turned inisible, even in other worlds.