Welcome to BPNet and please never apologize for long, informative posts when you are asking for help. It is really so much easier to offer advice if our members have information to work with like you provided. It's far harder for us when we have to deal with posts like "my snake strikes! why?" Providing housing, handling and information on this snake is really valuable so thanks for that.

The thing I'd say is this snake is young and simply acting as young snakes do. No matter the amount of handling, whether it's captive bred or not...it is and will remain an instinctual creature with all it's wild ways still fully intact. Things trigger snakes, sometimes as humans we'll never fully understand what the trigger at that specific moment was.

Sometimes a factor can be this snake's young age. Instincts tell young snakes that lots of things can eat them, so they tend to be more reactive and defensive. It's a survival mechanism at work. Sometimes it might be a bit too much handling or not enough, sometimes it's a sudden vibration or scent the snake picked up on, sometimes it's just a snake being a snake and 5 minutes later it's fully relaxed again. Sometimes it's hunger.

In other words, there's no absolute reason. Watch for patterns rather than specific single reactions. If the pattern is that this snake is acting up on certain days, maybe it needs to be upped on it's prey or frequency of feeding (a good digital scale is your best friend on helping you decide about that). Maybe it's not feeding but that day in your house is noisy and busy. I have snakes that will trigger defensively over something that will not trigger another snake so it's very individual as well. Learning to read a snake's signals, both subtle and outright, is part of the joy of sharing your life these amazing creatures.

I would also just say to always remain relaxed even when the snake is not. They may not be able to do higher math or bond with us like our pet dog does but I fully believe they are experts at picking up certain things. One of those things seems to be fear or anxiety in a handler. A relaxed attitude of "oh well you are just being a bit pissy hissy aren't you" really does help. Don't let the snake's attitude change yours, stick with habits and simple routines, these seems to help ball pythons be more easily handled.