While enchanting my armor, I enchanted a diamond chestplate with Fire Protection 4 and Protection 3. From my understanding and research, I am pretty sure that shouldn't happen naturally.
Steps to reproduce
1. Get armor
2. Enchant it
Linked issues
Attachments
Comments 2

This has already been reported, see MC-141961. Please search before creating a report.
Tested more in a creative world, attached them