What I expected to happen was...:
I would see a diamond sword glowing, meaning it was enchanted.

What actually happened was...:
The diamond sword's enchantment glint wasn't appearing, but in the hot bar, it was. Enchantments were there, but when held in main hand with an "ominous shield" (shield decorated with an ominous banner) in my offhand, the glint doesn't appear. 

Steps to Reproduce:
1. Defeat a Pillager patrol leader/Pillager Outpost captain.
2. Obtain his ominous banner.
3. Apply said banner to a shield and equip it in your offhand.                      4. Enchant and equip a sword in your main hand (or vise versa).                5. And viola, the bug is triggered. 

Also, I was using the default look of minecraft when I triggered this bug. 

(Note: This bug isn't limited to swords, it affects all enchanted items, including equipped armor.)