Issue occurs when 'Deliver On Full Approval' is ticked in 'Invoice Register Options'
When enabled the quantity delivered will automatically update, adding the quantity invoiced on invoice approval. This option should not be used if you are going to manually receive purchase orders.
This can be checked using the following steps
Login to FinOps Administrator
Go to System Settings, Purchasing, Invoice Register Options
On Settings, lower half of screen, left hand side
Deliver On Full Approval option is enabled if ticked.
Note: If you are thinking about changing this option and would like to understand the implications, please reach out to your account manager or CSM.