Quantity required to complete this transaction no longer available

 Hi All,

           Recently encountered with this error "Quantity required to complete this transaction no longer available"

             Checked the move transactions and founs that the errored quantity was still in the Queue of the operation sequence

           For clearing the error just moved the quantity to "To move" and resubmitted the transaction.

I am trying to understand the reason or Root cause behind this error?

Can someone please help me on this ?

Thanks in advance