Actually, our whole family is very happy with the Mumbi cases. Only this time the shell had clear signs of use. I have long wondered back then or not. I then selected the replacement. Good service from Amazon.
Addendum: Meanwhile came the replacement. Looked even worse than the first. I also got a replacement directly from HandyNow and behold, a perfect shell. The service of HandyNow was really great. Will order again from the dealer covers or sheets.