Difficulty popping particular snake..

I have been breeding Ball Pythons for about three years now and have never had much trouble popping any of my Ball Pythons, from hatchlings to adults. I have had decent experience with it over the past few years.

However, I have a Pastel Enchi who I bought as a male hatchling a few months ago. He is close to 500g now, and I have never been able to get full protrusion of his hemipines. When I try to pop him, I can see what looks like the red of the hemipines starting to bulge behind the scent glands, but never full protrusion.

Starting to wonder if it's possible he could have a problem with his hemipines...

Or is it more likely I'm still just not as good as I think I am at popping. Maybe he's just much stronger at holding them in?

Have you had males that you've had trouble popping compared to others? Just concered because I have valuable plans for this male as a breeder and have been trying to check for spem plugs and can't get hemipenes. I can pop any other male in my collection, bigger or smaller, with no problem.

Any input/advice?

I actually just went through the same predicament. I have a 600g male lesser that I bought at around 175g and never was able to pop him male. I was able to probe him male, but I couldn't see ANY hemipenes. Just after New Years, I threw him in with a female and woke up the next morning to a lock. He's been locking with two different girls ever since.

My only advice would be to find someone to help you pop him or probe him to double check his sex.