Usage of FAWE commands makes other players disappear for 1.9.4 client

[Miiteee]

'/viaversion dump' Output

https://dump.viaversion.com/5a9405b1d4eeeace776bd4c86dcc38eeffcaf93c700a9bea643c5c8d2b6490f9

Server/Client Error

Bug Description

When executing a FAWE command that instantly changes a block to another (such as //set, //cyl, //replace, //undo), all nearby players disappear for a 1.9.4 client. The only way to get the players to show up again is by waiting some time, which doesn't always work, or reloading the chunk (not with F3+A, but literally getting far away from it and coming back). Rejoining also does the trick as it reloads the chunks.

I'm pretty sure this also happens with versions newer than 1.9.4, maybe up until 1.14. Can't confirm, though.

Steps to Reproduce

1. Install the latest version of FastAsyncWorldEdit on a 1.21.4 Paper server alongside ViaVersion and ViaBackwards (5.4.0-SNAPSHOT)
2. Log in the server using two clients: one using 1.9.4 and the other on 1.21.4
3. Make sure both players are next to each other
4. The 1.21.4 player must select an area with the WorldEdit wand and execute the command //set dirt (can be any block).
5. Said player will become invisible on the other player's end as soon as the command is sent.

Expected Behavior

No players should disappear.

Additional Server Info

My server is running on Paper 1.21.4. I'll send a screenshot of all my plugins below.

Checklist

• Via plugins are only running on EITHER the backend servers (e.g. Paper) OR the proxy (e.g. Velocity), not on both.
• I have included a ViaVersion dump.
• If applicable, I have included a paste (not a screenshot) of the error.
• 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	❌
Platform Type	unknown
Is Proxy	❌

[Miiteee]

Plugins that I'm using:

[Kichura]

Does this continue with 1.10 too?

[Miiteee]

I actually thought it'd be best to answer this question fully, so I went ahead and tested with every version until the bug didn't happen anymore. I found that it continues only up to 1.13. In 1.13.1 it's 100% normal.