Summary
An old bug that was being experienced mid-late 2023 has resurfaced. This bug affects several games using the same system to simulate subway trains. The bug causes train cars to randomly disappear, breaking the train (because it obviously should not happen!). See the link below for my bug report on this bug when it first appeared:
This issue was first reported again yesterday (2/15/2024).
The original suspicion was that the bug was related to part streaming or constraints, but this is not certain.
Reproduction Steps
The wheels/trucks/bogies of the train are attached to the floor/base/body of the train using a HingeConstraint.
Operating a train in the games affected will have the bug appear randomly.
Expected Results
All train cars should exist as normal and nothing that is out of expectations should happen to them.
I would send the video file itself, but it’s too big to upload!
I am not sure what you mean by that. Do you mean server side test in Roblox Studio? I am not sure if it occurs in Roblox Studio. As mentioned by G4m1ng, player count could have an impact.
All the trains are server owned network ownership? Is this set immediately upon game start? The reason I ask is that if you don’t do it before players arrive, they can “take” over the network ownership just by being near for some reason.
I believe they’re set to the driver, then set back to server when they leave the vehicle seat. Regardless, this means that every time it happens, the train already has a driver (trains without drivers are deleted) and its network ownership has been set to the driver.
While in game, just one player, turn on performance stats in settings (doesn’t need to be studio mode either), see what the receive bandwidth is while no train is moving. Then start driving a train and see what it will max out at.
But the thing is that I believe the train car disappears when the train is stopped, and/or possibly the moment after it stops. I’m not sure if it has happened in motion.
I had a lot of fun testing this with a friend. I was on PC, max details, max frames, no issues running trains around with them on board. They were playing on mobile, so I had them spawn a train so I could ride with them. The first thing that happened was the train fell apart. So, I had them spawn another one. This time it worked, so I got on board, took a seat and just watched as they drive it. They told me that had to reduce their detail settings to 1 to be about to drive. That was perfect actually, I wanted to see what happens when the client struggles to network own and drive the train. So they drove around for a little while, it was very slow, but it was working. We got above ground and told them to start maxing out detail settings to see what happens. After a few seconds the train came to a glitch stop and started to fall to pieces again and they eventual crashed their game, haha.
I think your issue is probably more to do with the clients and bandwidth limitations causing issues. While I was zooming around on my PC, I was easily hitting +68 KB/s the entire time. When I had my friend drive a train, I could tell they were struggling as the bandwidth would drop to 20 KB/s and then spike to +55 KB/s and the train would either move smoothly or stall or shot forward real fast. Good thing I was attached to the seat that time.
So, every-time seems to be fine when the client running the train has a fast connection and fast computer, but through in a slow device or limited bandwidth and funny things happen. Might really be beyond your control unless you switch the network ownership to the server and make the clients use drive controls instead.
Myself driving with the entire map loaded into memory, max distance, etc.
I think something changing on Roblox’s end is ultimately causing it as this bug originally did not happen. It first appeared, then it stopped appearing (it was somehow fixed, though likely unintentionally), but now it has returned.
If it really is dependent on client, then that sucks because it just adds on to the list of potential issues that can be caused by a client’s connection or performance. But I’m hoping that this can actually be fixed, seeing that it did not happen originally and was even fixed once.
I agree, it is Roblox, but I was about to reproduce this myself again today by ramming my train into the back of someone else and it caused my train to start to fall apart and the parts continued to float out in space and move along with me when I was driving my train. In this case, it was the doors on the side and my train was still moving until it finally flipped off the track because the doors got “caught” in something out in space.
When this bug happens, does the missing part of the train look missing for everyone or just a single player? (Trying to rule out “Local Simulation vs Authoritative Simulation” desync)
Is there a freeze/long frame when the train car disappears?
So, I had them spawn another one. This time it worked, so I got on board, took a seat and just watched as they drive it. They told me that had to reduce their detail settings to 1 to be about to drive. That was perfect actually, I wanted to see what happens when the client struggles to network own and drive the train. So they drove around for a little while, it was very slow, but it was working. We got above ground and told them to start maxing out detail settings to see what happens. After a few seconds the train came to a glitch stop and started to fall to pieces again and they eventual crashed their game, haha.
