Enqueued Job being run indefintely

I am using .Enqueue() to fire-and-forget a job. In this particular case the job is being run indefinitely. I can confirm it’s only being enqueued once and that no uncaught exceptions are being thrown. It seems the job just keeps getting processed over and over again by different workers. I am using SQL Server for storage. Any idea what may be going on?

Turns out that the object the method was returning failed to Serialize.