If you pick in waves, you likely have some sort of conveyor sortation process to separate out the picks in order to prepare the shipments for delivery to your customers. Full pallet picks are normally picked separately and moved to staging locations awaiting the full case and split case picks. Full case picks are likely sorted to divert lanes assigned to a carrier or customer (ship to location or order depending on requirements).
The assignment process of requirements to divert lanes implies that the divert lanes are resource constrained, meaning you can only include into the wave a number of containers (full cases or split case picks) that match the number and size of the divert lanes. So you need a WMS or WCS to build the wave for you in a manner that controls these resources.
The diverts lanes will either be directed to a destination (palletization station or direct load lane) that may or may not require separation. For example, orders shipped by a parcel carrier, like UPS Ground, or Fed Ex Next day do not require separation other than only one carrier/service per divert lane. LTL and TL shipments normally must be palletized by order or ship to location.
This need to manage the fixed number of sortation resources available in the facility can be the problem. You may only have the ability to sort one order at a time to many of these sortation divert destinations. This means the person at the end of the divert lane is working to palletize the products presented by the sorter but cannot finish the pallet until all of the waves requirements have been sorted. This requirement for a fixed segregation between waves is the problem.
Many facilities employing fixed segregation between waves may see productivity on their sorter decrease near the end of the current wave and go to near zero until the next wave is released to the sorter.