Kanban assembly materials not driving PO suggestions

I am noticing that some purchased parts whose only demand is against subassemblies that we use Kanban replenishment for are not driving any PO suggestions when MRP runs. However, if I run the Generate Suggestions process, they will generate as normal. Some parts that are used in both Kanban managed subassemblies as well as other traditional managed assemblies seem to plan just fine. It’s just the parts that are strictly used in Kanban managed subs. Any thoughts here?