GMAsterAU

I figured it out. It was a user script that was running at array start up. It was writing to a path driectly to cache and as such I guess interrupted the formatting process. Once I disabled it and then ran through the steps it worked.
 
For future reference: 
- empty cache
- turn off Docker
- pause all userscripts writing to cache on array start
- stop the array,
- click the first pool device and "erase pool"
- set the filesystem and profile you want
- start the array,
- format
 
 
Thank you for your help