Jobs falling off schedule when adding parts

We add parts to jobs after the job is scheduled. We schedule the job before releasing to the floor -
this allows us to hold the production slot for the upcoming job while it’s in the approval process-but not ready for production yet.

Today we confirmed when we add a phantom part to the job - the job automatically is removed from the schedule.

Has anyone else experienced this? Any work arounds we are missing? We are looking for a solution - for the job to be scheduled and stay scheduled even when parts are being added.

At this time, we don’t run MRP or have Global Scheduling set up. Our production environment doesn’t fit well with either of these options.

Thanks in advance