Players Falling Through the Ground on Login, World Change, or Teleport

[fantahund]

Describe the bug and how to replicate it

Title: Players Falling Through the Ground on Login, World Change, or Teleport

Description:
We have been using Grim for the past few days. After initial issues with a large number of false logs, we managed to get it running somehow.

We have granted all players the permission grim.nosetback, which should prevent them from being set back. Despite this, the following bug is occurring:

Bug: Players fall through the ground when:

• This bug does not always occur but happens frequently enough to be a concern.
• Logging in,
• Changing worlds, or
• Rarely during teleportation.

This happens specifically when the ground is only one block thick.

Expected Behavior:
Players should not fall through the ground under any circumstances, especially when the grim.nosetback permission is applied.

Steps to Reproduce:

1. Grant the grim.nosetback permission to a player.
2. Set up a scenario where the ground is only one block thick.
3. Have the player:
   • Log in,
   • Change worlds, or
   • Teleport.
4. Observe if the player falls through the ground.

Environment:

• Grim Version: [current Version from main branch]
• Server Version: [Paper 1.21.3]

Additional Notes:
We would appreciate a quick fix for this issue. If there are any checks that we can temporarily disable to work around this problem, we would also be grateful for that information.

Grim version

current build from main branch

Server version

Paper ~ 1.21.3

Plugins

GrimAC

[SamB440]

You could try disabling https://github.com/GrimAnticheat/Grim/blob/2.0/src/main/java/ac/grim/grimac/manager/SetbackTeleportUtil.java#L358, note that this will expose your server to disabler exploits.

Personally never seen this happen though, the server always sets the player back when they fall through the world

[fantahund]

Hi,
Thanks for the response. We tried it out, and it looks good so far. Perhaps there’s a way to add an option in the config or a permission for it?

[SamB440]

No because it literally means people can "disable" (bypass) the anticheat. You need to figure out which part of that method is triggering the problem