6 caudal scales would be male if you are doing it correctly. That being said: You could read wrong if you are holding the probe at a bad angle as the snake struggles.

If you think they are both male you can put them together in one of their cages (supervised) and see if they start doing the ball python mating contest combat (look it up). They may not. If both snakes freak out though and try really hard to get away from each other-that would be another tip that they are probably both males. If they start mating: That is another tip...Getting someone who knows what they are doing to sex the snake is still your best bet.

I have bought several 'female' snakes from some of the most reputable dealers over the years and they probed as males when I got them. Most of the dealers were cool about their mistakes, a few were not (understatement). I only buy males now and hold back females I produce-a lot less aggravation.