Strange tool WeldConstraint interaction with vehicles?

I’m using this model (as a placeholder) in my game to test cars:

If a player gets into the car with a tool that uses a WeldConstraint, it gets stuck driving backwards for that player. Furthermore, this will happen with any car the player gets into after (regardless of whether or not they’re holding the tool).

Am I misproperly using WeldConstraints? If so or if not, how do I solve this?


  • the tools use a single WeldConstraint to weld a muzzle location brick to the handle
  • the tools are not massless, but being massless does not appear to solve the problem
  • I’ve tried some other car models, it seems to do the same thing for most of them

I’ve done some experimenting, it’s definitely an interaction with the WeldConstraint.

I can’t tell if it causes a weird thing with the player, the vehicle, or the vehicle seat. There’s no odd velocity or rotvelocity anywhere either. The only odd thing is the vehicle seat seems to think the throttle value is -1.

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I cannot replicate this. Can you provide a minimal file that reproduces the issue you’re seeing?


Sorry for the delay.

I was able to figure it out while trying to create a repro. It was due to using ContextActionService to bind a crouch animation to the gun. Not entirely sure why yet.

EDIT: Apparently binding ButtonL2 causes it.

Not sure if bug or I’m doing it improperly.

It is a Roblox bug caused by ContextActionService.