WIP Mass Load fails One or more of your scheduling dates is missing or invalid

We are on 12.1.3 and laod wip_job_schedules_interface table to update completion dates on existing work orders .For some reason the wip mass load has been failing consistently with this error .The same thing works in testbut does not in production and has been working for many years now.The only thing that changed was that we had to terminate the wip mass load once due to the size of the batch it was processing and divide the batches into smaller numbers by assiging different group ids to the one whole batch.

We are using the following values:

load_type = 3 Update Standard or Non-Standard Discrete Job