I have just purchased a 2009 XF V8, it runs great but once in a while and not all the time when slowing down at traffic lights or stop sign there is a hard down shift into the lowest gear.
Anybody had a similar issue and what was the fix?

 

Howdy Tango!

You've posted previously in the correct x250 forum which is where your 2009 XF gets better answers from fellow 6-speed automatic members..

https://www.jaguarforums.com/forum/xf-xfr-x250-44/

This x260 thread is for 2015+ XF's with 8-speed.
Best hopes for a speedy recovery.
Your ZF tranny fluid & pan filter been replaced?