Just going to add a bit more to my previous post.
Some years ago I had a Peugeot 406 hdi and it developed a similar problem...no one could find the reason.
After a lot of phaffing about, it was discovered (at MOT time) that the bushes in the lower wishbones were seriously worn, allowing lateral movement...every time I went over a bump or uneven surface, the driveshafts were being pulled out of the place they were designed to stay in. Apparently the 'end float' measurement is pretty critical, but a rebushing exercise took place and the problem vanished!
I hope all this helps you get rid of the problem....something to look at anyway.