I'd say if the croissant is problematic, it's unlikely that in each of those flight only ONE of them is problematic out of so many croissants baked by CPCS and LSG (since you mentioned both CX and KA) and you're so lucky that you get them EVERY TIME...
Actually I want to ask more:
1. Is it only on flights departing HKG or no matter where it departs you have this problem?
2. Have you tried on any single CX / KA flight that dropped the croissant and do you have any allergic syndromes?
3. Have you tried a croissant on other airlines leaving HKG where they use CPCS or LSG as cater?
Just want to help you to identify the real cause of your problem... The last thing I want to see from the news is one day a flight needs to do emergency landing because a passenger gets serious allergic reaction up in the sky...