CV Joint Shaft Shearing

This actually relates to a 1996 V70 mk 1 but as the running gear is the same as the 850 and there seem to be more CV joint related posts for the 850 I thought I would post here, hope that is okay?

I have sheared 3 CV joint shafts in around 300 miles, the last one lasted about 30 miles!
They shear in the same place each time about 1/2 inch fom the end of the splines just as it protrudes through the hub on the hub nut side.

I replaced the outer CV joint the first time and the whole axle complete with inner and outer CV joints the second time.

There has been a slight wobble when breaking, feels like a warped front break disc but that seems to check out okay.

any adivce appreciated as to what may be causing this strange and expensive problem.