The UpdateConfig restart_theshold  setting does not appear to deliver much user value as it's highly sensitive to scheduling performance and may result in aborted/rolled back job updates when set too low.
Some background: This timeout controls task transition from PENDING to RUNNING during the job update. In the event of cluster capacity shortage, assigning a task to a host may take considerably longer thus expiring the timeout and depending on the failure settings causing an unnecessary job update abort or rollback. It was meant to give users some protection against unsatisfiable resource/constraint requirements. In reality though, it proved to be rather an annoyance to users when an update is interrupted due to unexpected delay in task assignment.
Consider deprecating and subsequently removing this setting.
This ticket tracks a first step to ignore this value in the scheduler updater. See linked tickets for follow-up work.