I had the exact same issue, see my thread about it here:

https://xoutpost.com/bmw-sav-forums/...lowing-up.html

It turns out that Arnott may have had a bad batch of E53 struts where the crimp ring isn't to spec. They have since resolved the issue and are sending me out new struts.

Their customer service has gone above and beyond, even received email updates from the CEO Adam, who personally saw that the issue was resolved.

The new struts are coming today, I will install and report back if all is well.