tmp file became empty if save during processing

[shir]

I use carrierwave_video gem to process uploaded video and carrierwave_backgrounder to make it in background using delayed_job. I want to know about video converting progress and carrierwave_video have a callback for it. In callback I update a column with converting progress and save model, in this case I see in logs that file_tmp is also updated and became nil and next processing commands fails because can't find file. I'm using store_in_background.