VM Export of AMI is not Completing

I would like to be able to export and import AMI images. To do that I am using the VM Import/Export CLI commands.
This is the first time I am attempting to do this, so it is likely that I've done something wrong.
I initially had some issues setting up the vmimport role and policy for the target bucket, but the command executed with no error.

I used the export-image command, and it seems to have been successful.
The ExportImageTaskId is export-ami-007dd383c413ab2ca.
The AMI being exported is backed by a 40GB snapshot. Typically creating an AMI of this size takes about 5 minutes.

When I run describe-export-image-tasks it reports that it is 85 percent complete / active / converting.
But it has reported the same information for the past three hours.
It jumped to the 85 progress level almost immediately after starting the export job and the information has not changed since.