What behaviour is expected:
If you have custom heart containers (example 40 not the default 20) when you join you can see all containers filled in base of health.

What behaviour is observed:
When join (you have full life) the client only show 20 hearts filled and the another 20 not filled, if you take damaage then the client reload the rest of containers full in base of health.

Steps/models to reproduce:
1. Join to the server
2. Run this command `/attribute @s minecraft:generic.max_health base set 40`
3. Get all the containers filled
4. Disconnect from server
5. Reconnect to Server
6. Take damage

Plugin list:

N/A

Anything else:
Gif of issue: https://imgur.com/rp8sWqA

Gif of vanilla working: https://cdn.discordapp.com/attachments/714744229611700288/779825899939561482/2020-11-21_18-41-00.gif