Unfirm sales order releases and their relationship with MRP

I need some help from the experts here, this is the situation: we deleloped a process where we would enter a customer's blanket order as release 1 on a sales order as an unfirm release with Qty Lock = true then ship with new releases as requested. The supply side is controled with min on hand and order multiples.

This appears to be working as planned for items that are purchased and resold, but on the make parts we are getting a unfirm job that drives a purchase suggestion on the buyer's work bench for the raw or components.

Has anyone else ran into this issue and if how was it resolved?

Thank you in advance for your help,

Bill