My current theory is that it's interesting programming choices, they've had the Jump modules cut to make space for, variously, Extra Eyebrows, Extra Cussedness or Extra Fur Distribution. More seriously, Pandora is just a bit fat and lazy, and Jyn has always been weirdly timid for a cat, she's quite tentative in the usual kitten activities which might involve flinging herself around the show. Vet checks have never picked up anything concrete, but I suspect she may have either balance issues or slight muscular weaknesses. I am fairly accepting of having Cats who simply don't Cat at full power in that particular aspect of Catness.