Possible causes for negative picked bins?

We are using RF-Smart for our picking function and Pacejet for our packing function. RF-smart will pick from bin ” A1-1″ and move to “Picked 1-101”.  When the order is finished packing, Pacejet is trying to write back to Netsuite, but Netsuite is throwing back an error

{
“TransactionID”: “3395603”,
“Status”: “Error”,
“StatusMessage”: “Netsuite is reporting a user error. The following Bin numbers are not available: Picked-1-101.”
}

what could possibly cause the items in  the picked bin to no longer be available?