I've tried placing doors in stacks and individually, but the customer just gets a 'out of stock' message. Same customer then tried to buy doors at Shavingfoam's shop also on SMP5 and had the same problem.
Chances are ....these are "new" doors ....the ones of diff. types of wood. I have found that, the new Door styles ....none of them are recognized in the realm of the normal "rules" of MC of yet. Meaning ....you can't lock them, or private them, and only the original Oak Doors are within the bounds of the MC rules at this point. I would use the [slot 1] technique ....have one in the first slot before placing the sign. If I read correctly above, you have already tried this, and I have found some of the newer items to be a bit glitch in this regard. The Pot O'Gold promo was one that caused many to experience this. I suppose in the realm of "thing to be fixed (or addressed)" this would fall way down on the list for Mojang, but I'd like to think at some point it will behave normally.
I'm not too sure there. The shop & lock mechanics are custom EMC routines. And because these doors have different item ID's I suspect that the locking part simply doesn't recognize these because of those new item ID's. I don't think there's much to fix for Mojang here because in vanilla gameplay these doors behave as they should.
Doors of any type can't be locked. I just tried it - a lot. As for shops not working, that's a bug, but a temporary fix is to sell using slot signs. Edit: Seems new doors don't work with access signs either/
It's NOT an Empire thing. My experience is across multiple Servers .... where the new Door types do not work properly. I've run this experiment ....and found, that to do what we would expect - in any capacity - the Oak door is the only one which "behaves" as we would expect.
Were they ever able to be locked? I will try and get these doors working soon. Red Sand is also on my list. Any new shop issues people know about?