Light block appears as air when submerged in water

[Kichura]

'/viaversion dump' Output

https://dump.viaversion.com/51a2744226eb330df21c792452175609a6c4730e325f8348ba772514d49c974a

Server/Client Error

(No errors have appeared on both clients nor server)

Bug Description

When placing a light block in any water source such as in a lake, The light block will appear as air when playing on 1.12.2 client:

Steps to Reproduce

1. Make a clean 1.21.6 server,
2. Log on with a 1.21.6 client,
3. Place a light block in water,
4. Relog to 1.12.2,
5. Notice the light block being air instead of water.

Expected Behavior

Light blocks in water remain as water.

Additional Server Info

1. This server does not use any proxies,
2. This server uses Paper 1.21.6, (Build 6)
3. ViaVersion & ViaBackwards 5.4.0-SNAPSHOT with 1.21.6 support.

Checklist

• [x] Via plugins are only running on EITHER the backend servers (e.g. Paper) OR the proxy (e.g. Velocity), not on both.
• [x] I have included a ViaVersion dump.
• [x] If applicable, I have included a paste (not a screenshot) of the error.
• [x] I have tried a build from https://ci.viaversion.com/ and the issue still persists.

[Barvalg]

Athena Log Analysis

Platform Information:

Property	Details
Contains Via	:x:
Platform Type	unknown
Is Proxy	:x: