This update changes the equipment system. To put it simply: the synchronisation between armor stand and inventory is now removed because it was prone to errors and I had to build in a delay in order for it to be dupe-safe. But even with the delay it wasn't and that's why I changed it now.
The new system is de-synchronised, which means that the changes made in the inventory are only applied when the inventory or the page is closed. Of course other players can't add/remove armor while a player has the inventory open.