I think I found a quirk in my 2004 XF. I noticed a pattern that might be caused by disconnecting the battery while I work on the XF.
Upon reconnecting the battery, I have noticed that the turn signals no longer work. If I push the Emergency flasher button, all four corners flash as they should. Then, after turning off the Emergency flasher, the turn signals work again as they should.
This has proven true several times.
I don't know why yet. Software/firmware feature maybe. But it works.
I thought that I would pass this info along to the group.