The error is
An uncaught exception was raised: [Errno 2] No such file or directory. The problem seems to be due to the extra fake CD drive that’s included on this particular USB stick. When you insert it you will see the expected removable drive but there will also be something called U3 System which appears as a CD drive, it contains some Sandisk utilities. The error occurs even if you select the correct .iso instead of the default U3 drive. The solution is to unmount the U3 drive.
Reformatting and repartitioning the drive won’t remove this extra drive but there are tools to do this. u3_tool works on Linux and can be installed as a package in Ubuntu. I ran
sudo u3_tool_sg -p 0 /dev/sdb
which seems to have done the job.
There’s also an official removal tool for Windows or Mac.