John the ripper gets password on the first iteration but never again

I have a shadow file with the following password hash (password= toor)

root:$6$0w9WRuc5$ldas/kVEO40xeKnzBTWvt4IKMIQN2a5/eQ1xfKWC.6Hns19UNZVnj0KNt87CHOiiz2dq00klFUsVJBKvGM7Ri1:16079:0:99999:7::: 

and stored in a file called shadow1. When I run "john shadow1" I get

john shadow1
Warning: detected hash type "sha512crypt", but the string is also recognized as "crypt"
Use the "--format=crypt" option to force loading these as that type instead
Loaded 1 password hash (sha512crypt [32/32])
toor             (root)
guesses: 1  time: 0:00:00:00 DONE (Sun Feb  8 17:34:46 2015)  c/s: 86.48  trying: R99999 - root
Use the "--show" option to display all of the cracked passwords reliably

However if I run it a second time it produces something different

john shadow1
Warning: detected hash type "sha512crypt", but the string is also recognized as "crypt"
Use the "--format=crypt" option to force loading these as that type instead
Loaded 1 password hash (sha512crypt [32/32])
No password hashes left to crack (see FAQ)

Why does it give me a different result. I am trying to test different John the Ripper options but I cannot proceed if I cannot even get the same results with the same command