Guys, I have re-read the posts and tried this again
On every enlarging lense I own (4 off Rodenstock Rodagons of various focal lengths) except the Schneider when I stop down the grain in the Peak stay in focus
With the Schneider the grain goes a little mushy when closed down 2 stops & comes back sharp when opened up again
The view on the baseboard stays looking sharp in both cases - to my eyes
I have not yet tried printing the image at both apatures - but I guess this is the next step and then examining the image with a lupe.
I don't know what has happened to the lens but I doubt it was designed to do this.
It is also easy to work around - I just focus when stopped down
However, if I need to produce top quality prints I will be using a different lens to the Schneider
Thanks for the help/sugestions & input