This alert message indicates that the drive you are exporting to is getting full. To address this, clear up some space on your hard drive or share to a different drive with available space.
Final Cut Pro X, Motion 5, Compressor 4: About the "Failed: Quicktime could not access a file. Offset too big" alert
When sharing to a QuickTime movie, Apple Devices, HTTP live streaming, or AAC audio, the following alert may appear "Failed: Quicktime could not access a file. Offset too big."