Hello,I've been investigating with your calendar file using libical3 on korganizer and I've found out that libical3.10 and libical3.12 are correctly importing your file, when libical3.11 doesn't, so I'm guessing your problem is fixed with the last package.
Can you test with package libical3 3.0.12-1 ? it's currently in unstable but I've successfully installed it on a ubuntu latest.
/Nicolas
