Constraint and Index disabling when job fails

Good morning,

    I need some clarification on the constraint part. We have a custom job that picks sales information and inserts into staging table. That staging table uses composite primary key and Index has been set on those 2 columns. For some reason, the custom job was failing during the insert.

    On analysing, we found that, the job was failing when it was trying to insert into the history table. Also we could see, the constraints and index in the staging table gets disabled.

    We checked from backend and could see no job that disables the constraint. Is there some other reason that disables the constraint from staging table after the job fails.