I actually have never been hissed at. I have been bitten by multiple snakes I've had in my life, most of them being wild caught local stuff when I was a kid. My BCI girl did head butt my hand when she was a baby and new but since then she has never shown any anger. When she wants to be left alone, she will go sit in her hide box, or if I try and pick her up, she will just crawl back into her cage. That's when I just leave her alone. My BP doesn't seem to care either way and is like a pet rock. Is your snake might be getting rdy to shed? That's the time when both of mine get the crankiest if they are gonna get cranky. And I'm surprised your gets cranky on poop clean ups. My BCI girl seems overjoyed when I clean out her poop. If there is a poop in her cage, she gets antsy and paths all over the cage like she is trying to get away from it. Then when I clean it, she calms down and usually curls back up under her RHP.

If everything with husbandry is the same and correct, I wouldn't worry about it and just chalk it up as the snake is having a bad day and just leave it alone till the next day or so.