If you do the mech up tight, the mech doesn't rotate properly - if you push the upper jockey wheel backwards, it stays there, and doesn't return to its normal position
suspect the bush / pivotty bit is full of salt and crap.
Is it worth taking it apart and cleaning up? I think I have done this before and it was a right pain getting the spring back in
it's a Shimano 105 btw
thanks
Rather than take it apart (you can do it, but swearing and skin loss is an integral part of putting it back together), try drowning it in WD40 whilst turning the pivot / mounting bolt, that should free it up quite a bit, then once its free follow through with some thicker lube like chain oil or similar.
yes - I think I remember the swearing and skin loss bit!
Think I'll go for option 2!
all good now anf knuckles intact - thanks!