How to handle Roblox changing aspects of my character models in seemingly mysterious ways?

[tenIetters]

I am not sure if this behavior is documented anywhere or well-understood by anyone, so I’m currently labeling it as “mysterious.” There seem to be workarounds for some of the behavior I’m seeing, but I would prefer to know the root cause and implement a proper fix.

Weird thing #1 is that Roblox is adding a Motor6D object to a specific accessory’s handle when the game runs.

Here is a screenshot of the model holding an animation where the left arm holding the shield is supposed to be slightly bent at the elbow so that the shield stays parallel to the body:

As you can see, the arm is not bent in the desired way. The culprit seems to be this LeftElbow Motor6D that gets added in at runtime (it is not present initially):

If I manually delete this LeftElbow object at runtime using any method, the animation corrects itself:

I would like to know if there is some reason for this behavior. Currently I can go through my models and delete these things once they’ve been added in, but this is tedious and liable to happen in other cases as long as I don’t know the reason why it’s happening in the first place.

Weird thing #2 is that Roblox is altering the HipHeight value of a different model’s Humanoid when I parent that model to workspace, which causes the model to sink into the ground.

Here’s an example of how the model looks when it’s sunk into the ground:

I just made the model look like a zombie for the screenshot. The rest of the original model’s armor does not seem to be causing any issues, but the leg armor (the black bits at the bottom) do seem to, since when I remove that part of the armor the issue goes away.

The HipHeight takes this value when I copy the model into workspace and run the game:

The initial HipHeight value is the default:

Manually resetting this value to 2 does not seem to work perfectly. When just running the game (not testing it; i..e, not inserting my player character), the issue disappears, but when I test it (using my player character), some models (but not all) still show the sinking. So, my current solution is to just completely remove the 3D leg armor from this model.

Any help with either of these issues would be appreciated, even if the root causes are not known. In particular I would like to know under what circumstances Roblox will modify properties or instantiate objects inside of character models without my knowledge.

[tenIetters]

Bumping this.

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[maxim01689]

Does this happen in live game?
To me, it sounds like a plugin issue, if you have any plugins, try to disable them and fix your models if they are bugged in studio (Edit mode) and test

[WishfulElena (Elena)]

You cannot use RigAttachments for Accessories, it conflicts with limbs. Use the LeftGripAttachment or LeftShoulderAttachment and offset accordingly, and the FootAttachments for the bottom part of the armour.

[tenIetters]

Thank you, this does seem to have been the source of both issues. The leg armor was using LeftKneeRigAttachment and RightKneeRigAttachment, and the shield was using LeftElbowRigAttachment. This caused corresponding Motor6D objects to be created in the handles, which presumably led to interference with the limbs.

It may be possible to use the existing non-rig attachments instead (LeftShoulderAttachment/LeftGripAttachment, LeftFootAttachment, RightFootAttachment), but I had difficulty getting the accessories to stay in place, since the shield is really meant to be attached to the left lower arm and the leg armor to the knees, not to the hands and feet.. So, I have done the following instead:

1. Renamed all rig-type attachments in the accessories to something custom, like ShieldAttachment for the shield.
2. Created a copy of this attachment with the same position and orientation in the body part of the model that the attachment’s handle is welded to.

This seems to have solved my issues without needing any further adjustments. I have not tested this with players, but I am hopeful that I can instantiate these custom attachments in the player character models when they spawn in.