hmm to my knowledge I haven't grouped anything in this scene. I tried ungrouping the object but it just knocked it out of the hierarchy. I tried moving it again and the same effect happened even outside of a parent group. looking at the hyper shade its shape is only connected to the initial shading group.

I then tried grouping the object but the same thing happens even under central rotation

I've even tried re-modelling the finger tip but the same effect happens

its strange because the other two segments of the fingers work fine it's just the tips


Thanks for your help anyway

edit:
Ahah! i finally fixed it. i duplicated the joint above the second knuckle and replaced the existing tip joint with it it now seems to work! its odd because thats how i made the finger in the first place but ho-hum at least it works!
thanks again