Interesting - I’ve never seen one crack like that. We see hairline cracks right around the threaded inserts occasionally, but never through the entire nozzle. What screws did you use to attach the thruster and how tight did you tighten them? If the screws were too long they will push directly on the plastic as you tighten, which could cause this.
Please email me and we can see what we can do about getting a replacement sent out to you.