minecraft:equippable doesn't work fully

Partner Rank: 3

Verification Builds: 1.16.1

Regression Builds: 1.14

Summary: Slot 2 in the minecraft:equippable component doesn't work

Affects currently Live Content: Yes

Impact: On our map Advanced Dragons, Dragons are supposed to have three equippable items. The first two items work fine, the third one doesn't show up since 1.16. The respective entity uses format version 1.8.0, though it doesn't work in other format versions either.

Repro Steps: 

1. Create a world and entity with format version 1.8.0.
2. Add minecraft:equippable to the entity, using slot 0, 1 and 2.
3. -> Slot 2 doesn't show up in the Game

Observed Results: Slot 2 in minecraft:equippable doesn't work.

Expected Results: Slot 2 in minecraft:equippable works and gets displayed properly.

Screenshots/Videos attached: No