So here is the current (and hopefully final) status update regarding the inventory:
I have now replaced the old, dysfunctional inventory system with a new one. It should now be able to deal with ALL types of items and blocks. That means that you should be able to have banners, shulker boxes and all kinds of enchantments etc. in your inventory and enderchests without a risk of losing them.
ATTENTION: The Deposit and Shop still cannot deal with them since spigot (the server software) has a bug here that does not send the information properly to the system I am using.
The new system works a bit different from the old one: It is unfortunately less flexible. The old one for example shared XP across all survival worlds. The new one is simpler. You share ALL items (XP, health, enderchests, hunger) across the “normal” survival worlds: empire, darklands, nether, kingdom & aether, all other survival worlds each have their own, isolated set of those and nothing can be carried across. Let me know if the system does it differently in any sense.
I have done my best to convert existing inventories from the old system to the new one. It could be that some of the enderchest contents have been lost in the process. If you have significant contents lost from your ender chest, let me know in a comment here within the next 2 weeks and I will try to recover them. It’s quite complicated (not even sure how possible) to do, so please only do that if your lifeblood was stored in there.