parameters & udf's

Hi all,

can anyone tell me why the use of parameters & relations seem to interfere with the updating of udf's. I have an assembly which has relations & parameters, i have created a udf from one of the models in this assembly. Now what i am having trouble with is updating the udf, i can make a change to the source model, then open the part with the udf, click edit, udf operations, update all, then regenerate, but it does not. Here is the strange thing, if i delete the udf & re-insert it, it comes in with the changes. I have done some experimenting, creating udf's & inserting them into models with no parameters or relations present, & there is not a problem, everything updates as it should. Can anyone help me out?

Regards

John