Bulk Plan planning cost errors

Hi,
we have a problem with bulk plan planning and show routing option.
We understand that by planning 4 orders with the same location, they are consolidated into a single shipment with a much higher cost than if these orders were planned separately, for example: 3 orders in one shipment and 1 order in another shipment.
OTM should choose the best economic offer to lower the overall planning costs, but if shipments with a much higher cost are planned with the bulk plan, the meaning of the product is lost.
How can we solve this problem?

Thanks,
Davide