Fulfilment Workbench - Transfer Orders

We are multi-site with all the stock manufactured at Site A and then shipped across the country to Site B or C. We are having trouble with the Transfer orders in the fulfillment workbench I do not know if the issue has always been there or is the result of a recent update.
The line is showing 100% avail to fulfill the transfer order line is for shipment from site A/ Warehouse A but the Qty on hand/available is showing the inventory from Site A+B+C there is none in A and therefore they are getting pick errors when they try to reserve and release.
We are relatively new to the workbench has it always been like this? how do the users know which lines they can release for picking