This should not be a problem-
As a booster, the Komfort Kruiser does not provide direct restraint for a child. It raises the child and positions the seatbelt correctly, so the seatbelt can provide the primary restraint.
Bicycle helmet grade EPS foam is being used more frequently in child seats. Having an energy absorbing foam around the child's head and other areas is often considered somewhat safer than hard plastic. Of course, hard plastic is likely to be more durable, so there is a tradeoff.
In a crash, any child restraint or booster can be damaged and usually requires replacement. Again, with a booster, it may not be as significant since the seatbelt system is the primary restraint. As long as the booster is positioning the child correctly before the crash, then it has done its job. Obviously, if you find a broken part from everyday use on any child seat, you should contact the manufacturer immediately and see if a replacement is available.
You might also try to contact Jupiter and have them address your concerns directly. I have found their customer service to be very helpful in the past. Good luck!