Stiff Joints? (Beast Wars Fox Kids Dinobot)

Hi,
So I was transforming my Fox Kids Dinobot this weekend for the second time in almost a decade, and I noticed his joints were very stiff. Not the ball joints, but the Dino hip joint at the top of the leg which becomes the robot's shoulder. It's big and somewhat of a half-circle, and it's supposed to twist. It just would not twist, although I put a lot of force on it. I was afraid to force it much more out of fear it would break, but eventually I was able to twist it. It seems to me that this is way stiffer than normal, and I was wondering how to go about loosening it without having to resort to force, or just as bad, resorting to never transforming him again?
I looked up other threads about this issue but they all seemed to do with ball joints, not the kind I was having trouble with.
So I was transforming my Fox Kids Dinobot this weekend for the second time in almost a decade, and I noticed his joints were very stiff. Not the ball joints, but the Dino hip joint at the top of the leg which becomes the robot's shoulder. It's big and somewhat of a half-circle, and it's supposed to twist. It just would not twist, although I put a lot of force on it. I was afraid to force it much more out of fear it would break, but eventually I was able to twist it. It seems to me that this is way stiffer than normal, and I was wondering how to go about loosening it without having to resort to force, or just as bad, resorting to never transforming him again?
I looked up other threads about this issue but they all seemed to do with ball joints, not the kind I was having trouble with.