Ebay why?: combined shipping gotchas

I've learned a lot of stuff regarding ebay's combined shipping invoices during the past year.
Mostly, non-intuitive gotchas. Stuff which seems like it should work, but just doesn't work.

1. 30 days (or is it 32?) after sale, no item can be combined into an invoice. Even worse, seller can't send any invoice at all. Buyer can of course still leave feedback.

2. If the UID assistant files the UID, the item cannot be part of any combined invoice.

3. Sometimes for unknown reasons, the combined invoice created by ebay just doesn't include some items (nor does it offer the link to add more items).

===
Some suggestions to Ebay regarding combined shipping.

1. If an item is part of a combined shipment, don't lodge a tracking number strike until 24 hours after the last item in that package is paid for.  That's what both buyers and sellers want.

2. All unpaid items to a particular buyer should be available for combined invoice.

3. If the UID is filed, create a way for seller to return the item to ordinary unpaid status, so that the item can be combined on an invoice.