Opportunistic streaming breaking when replicating strong springs of physical assemblies

Originally this bug was reported almost a year ago under this announcement post: Stream Out Behavior: New Property for Streaming Enabled - #133 by OneSkyVed
I did get reached out by a roblox employee, but after a lot of discussions the conclusion was that this bug was not really possible to debug as it happens absolutely randomly unrelated to any user input. This also meant I could not narrow down what caused it, until recently

How to replicate the bug:

  • Join the game (OneSkyVed's Trolleybuses Place (indev) - Roblox)
  • You can afk, but you MUST be on a server with other people, and other people MUST be driving around (in order for next step to work)
  • When someones vehicle enters your streaming radius, sometimes with absolutely random chance you will see how vehicle model got split in 2, one part flies in the air where the model firstly replicated in, and second part is the one that replicated correctly
  • I should mention that the person who drives the vehicle sees his vehicle perfectly fine, it is not broken for vehicle owner, only for the person to who the vehicle got streamed in

Original screenshots are provided in my original post. Also originally touching the part of the vehicle that is flying in the air caused your character or your vehicle that you were driving to get flung into nan (everything starts flashing and you lose control of the vehicle)
Videos of original version of that bug:

Notice how I call it “original version”, that is because I did an experiment, and used some tricks with roblox physics, and separated my model of the vehicle, which resulted in part that breaks not affecting the entire vehicle. Because of that current version of the bug does not cause you to get flung to nan, so in current state for my game its just a visual bug that does not affect gameplay anymore. This is how it looks now:

This issue occurs very often, but is completely random, and probably depends on network speed/lag
Originally this issue was ruining the game, as touching broken assemblies also made it so your own vehicle will break (get flung into nan). After I separated vehicle model into 2 parts, this issue became purely visual

The reason why I know that it is a strong spring, is because springs are almost the only things that can cause physical assembly to get flung into nan, and in new screenshots you can see how model of a pole (stick on the roof going up) is the part that is breaking/flying in the air, and that is exactly the thing that has pretty strong springs that do not break for the driver, but break when getting replicated to other people

Expected behavior

Vehicle to get streamed in properly, meaning everything is intact and will not randomly remain flying in the air

This is how a normal vehicle should look like:

A private message is associated with this bug report


Thanks for the report! We’ve filed a ticket to our internal database and the team will look into this. Also we’ll keep you updated!

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I should’ve replied to this earlier. I’ve actually been discussing the issue with OneSkyVedOneSkyVedOn in a private message since they were sharing place files and other info.

I believe I have a fix that is going through the review process right now for one of the main problems. Trying to investigate the secondary visual problem.

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Has this fix been pushed through? I’m starting to see this issue with default streaming settings



Place: Rhythm City- DEV - Roblox

I have two fixes to separate issues discovered while debugging. They are in flight that should be going through the QA process.

Earliest I would be able to enable them would be Thursday next week provided I QA doesn’t discover something I missed.


This is very interesting if your game experiences both of the issues that my game does, I wonder does this mean that both of our games do something similar that causes these 2 issues to appear? (Regions not loading it + this issue with physical mechanisms)

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I’ve encountered a similar issue with my game too which uses springs for car suspension.

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Funny enough, this issue happens regardless of if you have a vehicle and we don’t utilize much outside of attachment points for proximity prompts here and there. Maybe that is what’s messing with things? :thinking:

The two fixes @Khanovich referred to have been enabled since yesterday 4 PM PDT. Please let us know if you are still seeing issues in your experiences!


Hey! Sorry to be a pain in the butt but we were just able to reproduce the issue in this place: [DEV] Harmony Hills - DEV - Roblox

Streaming settings:

We were able to reproduce this with an iPhone 12 Pro on the latest iOS 16 build.

What version of Roblox App did this device have?

Hey! Sorry for the late reply. The app version is:

We’ve been also able to reproduce the issue more reliably on a 5th gen iPad with the same app build. Both devices running iOS 16.4.1

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