Reserving issue within batch order.

I have an item in which we scan into the system via Item Arrival then into a batch order which is used as part of the production line. Instead of doing that, I’d like to be able to reserve those batches and serial numbers to pull through from Stock>Reservation. I have created 2 different Reservation Hierarchies:

Hierarchy 1:
Site
Warehouse
Stock Status
License plate
Batch number
Serial number

This hierarchy wouldn’t pull through the serial number alongside the batch number. So instead of pulling through 100 serial numbers, there would be 1 line of 100 for that batch. Worked for 1 or 2 batches then stopped.

Hierarchy 2:
Site
Warehouse
Stock Status
Batch number
Location
License Plate
Serial number

This hierarchy is now giving an error message that the stock can’t be reserved because there is 0 available. Although the stock is available and all the dates within the picking list on the batch order are fine also.

Both of which worked in SOME scenarios. Hierarchy 2 is the current one I’m using, it worked for the first couple of batches I reserved. Then didn’t work for others, for the SAME item. Same item model group (nothing changed within it), same manufacturing dates, no expiry dates, no shelf life dates, same stock dimensions, both sitting at registered status.

I can’t see why it worked for 1 batch and not the other, there is no difference that I can see.

I’ve created the same order again within LIVE and TEST, same issue.