I wouldn't worry too much about the movement issues. As long as the snake moves well when it's in its cage... My female hypo thrashes like that when she is first taken out of her cage. Since I got her, it always seemed when handling her like she was VERY afraid of falling. She'd grip very tightly. It seems that the quicker I take her out of her cage (as in quickly grabbing her, before she has a change to try and grab onto her water dish or the door of the cage to try and stay in), the more relaxed she is. If she happens to grab onto something and I have to struggle to get her out, she is more "lashy", almost like she is panicked and is trying to find something to grab onto, and takes quite a while to calm down.
Since she does act differently than my other boas, at first I was afraid of IBD or a neurological problem - but she is really just "afraid of heights". She does not stargaze in her cage, and she moves around just fine as long as she has a lot of support underneath her. So perhaps yours has the same issue - just not being used to handling, or needing to feel more secure when being handled.
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Lauren Madar
www.ophidiagems.com
1.1 Hog Island Boas
1.1 Hypo BCI
0.1 Sorong-type GTP
1.0 Normal Ball Python