Getting issue while merging shipment otm

Summary:

Issue in merging shipment with Optimize option

Content (please ensure you mask any confidential information):

The requirement is to merge the shipment with the optimize option . But when trying to merge its unable to merge shipment , though rates & itinerary are in place.
This option works fine we use manul shipment merge but when trying with optimize its fails .

Also the truck(equipment) capacity is within range of combined orders

Version (include the version you are using, if applicable):
25 B

Code Snippet (add any code snippets that support your topic, if applicable):