Dupplication of items in shulker box hold by zombie transformed into drowned

Hello, there exist an huge glitch of dupplication when a zombie than hold a shulker box (full of item) then it is transformed into drowned in a systeme of redstone.
Like that :

Killing zombies/husk while they convert into drowned/zombies causes held items to be duplicated (with redstone system):

https://www.youtube.com/watch?v=xVVwCF3Rmiw

Could you correct this huge bug of duplication please in order to keep safe minecraft.

Thank you in advance for your answer.

Best regards.