Error: Failed to assign service provider (0=null)

Summary:

We have recently configure a commitment allocation for our different service providers, to assign them a proporcional distribution of the shipments.

However, apparently due to this change, we are facing some trouble when trying to move one order release to an existing shipment, or one order movement to a shipment. The error we receive is the following:

The shipment dates match with the order release ones, and we can do a bulk plan with this order release and then merge, but the action move to existing shipment, which is faster than bulk plan and then merge, is failing

Can anybody help us to solve this problem? or at least find the origin of it?