That sounds like a problem with Android Platform-Tools.
- What OS and version are you running the script on?
- What’s the output of
fastboot --versionandmke2fs -V?
Since you are only failing the "wipe userdata" step, have you tried booting into recovery (fastboot reboot fastboot and select “Enter recovery”) and using “Wipe data/factory reset”? 
I’d still fix that problem on your PC afterwards if I were you 