It’s very complicated to explain this. So I would suggest you try and replicate the issue.
Create a brand new business and add inventory and delivery notes.
1st September, buy one laptop bag
2nd September invoice two laptop bags to client A
2nd September delivery notes two laptop bags to Client A
1st December, buy one laptop bag
2nd December invoice one laptop bag to Client B
2nd December delivery notes one laptop bag to Client B
20th April (new financial year, so set 1st april as new year), buy one laptop bag but don’t invoice for anyone
You will see in inventory-cost the laptop bag showing for client B and the invoice date will be 20th April not 2nd December, despite the fact that Client B has already been invoiced and received laptop bag. In inventory items, under quantitiy owned etc, you can see its wrong.
What appears to be happening is that if you if you buy one bag, but sell two, you are short one bag, so when you next buy a bag that bag is allocated to the client that is a bag short despite the fact that the delivery notes etc goes to the second client, so when you buy yet another bag that bag goes to the second client instead of the client who will be receiving the bag in April.
The best way to understand what I am talking about is to try and replicate the issue as suggested. I think that there is some kind of a bug.
But the most interesting thing about this whole issue is that Client A actually did phyically get two bags - however according to my invoice from the supplie and Manager, I only ever bought one bag! So I must have created a bag out of thin air or something!