That doesn't sound right. It looks exactly like the failure I experienced on my front Arnott Struts on my e53. See that video on it here:

https://youtu.be/gbd_EUJojyQ

This happened to me twice, in a row, with two new air struts from Arnott. The CEO got involved and emailed me directly, they ended up sending me two new struts free of charge to compensate for the saga I went through.

As it turns out, there was a bad batch of struts manufactured where the clamping force was below spec on those metal bands around the rubber bags. It looks exactly like what happened to mine. Mine burst with a crazy loud pop like a bomb went off- it set off the alarm and my neighbor's car's alarm. Thankfully no one was nearby when it exploded.

If you ordered yours from a third party, perhaps it is an older strut that was in the batch of parts that had the defect. Arnott told me they increased the clamping force spec on the E53 struts after that.

Should have taken photos of the markings to see if there is a date code on it. Arnott told me the same thing... could be an old unit that sat for a long period of time.