Cake wars issue chestplate

Hello! Cake wars is my favorite game in all of Minecraft. ever sense about last year every time I join a game on regular mode in Mineplex I am missing a chestplate. I can purchase one from the stores but if I walk about 20 blocks away from spawn it will disappear and I lose my armor points. this is a very frustrating issue and I've tried everything to fix it.. please help?

Thank you

Aimee Horan aka. crazyaimee101