I'm testing out hydra, for this purpose I started sshd on a Raspi with Kali 2 running as a target machine. The attacker is a Kali 2 VM on a Macbook. I verified that connecting manually via SSH to the target works.
Now I generated a password list of several thousand permutations with john the ripper's rule option, then reduced it with pw-inspect (to those with at least 8 characters). They all follow the same rules, e.g.:
Peter1234! Peter1234% Peter1235!
and so on.
Now I made sure the correct password is in this file. However, when I run hydra it reports in the end that it could not find the password. If I reduce the list in volume to about 30 entries around the correct pass it will work.
I'm at a loss what the reason might be and this way I can't pentest since I will not know if the password has really not been found or if it's my problem.