Physics in my game doesn't work correctly anymore

[ScriptOn (Genya)]

My game has these ragdolls which rely on the new Physics Constraints that came out like 8 months ago. I haven’t touched the place 4 days and I last played it 3 days ago. 1 day ago (yesterday) someone reported the game was acting funny. The physics seem to be half broken or something. My ragdolls no longer work in-game and I don’t know why.

I don’t know if this is considered Roblox Critical as it’s only a small portion of how physics work, but it’s definitely weird.

Here it is in local studio test-server as well:

Here’s where it gets weird. If I put just a regular ragdoll into studio and press play to let it drop, everything works except for the upper-torso. It’s rotation refuses to move or something, even if I tilt it sideways to make sure that it’s not perfectly balanced or something.

Here’s a gif (click to play, it’s green-screen broken but still works). The part that’s always going back to rotation 0,0,0 is called ‘Upper Torso’ and there’s no humanoid anywhere inside this model.

http://i.imgur.com/RUdlzvy.gif

As you can see he absolutely refuses to rotate, even going so far as to re-balance himself when I rotate him by studio tools. This has never happened before in the months that I’ve used this exact rig, untouched or edited. Not shown in the gif, but if I rotate by any other axis he’ll do the same thing: return to rotation 0,0,0

Here’s the explorer window, to show that there’s nothing physically inside except for constraints and the parts that they effect (Be sure to click on the first image to see the full list since discourse cut off half of it in the preview window)

[Darkmist101 (Darkmist)]

My brother brought this up yesterday when talking about our game bugging out as well.
Using BodyGyros seems unstable for us, players are not oriented as they were before.

[ScriptOn (Genya)]

We don’t use any body movers such as BodyGyro. Nothing but parts and constraints.

[Darkmist101 (Darkmist)]

I should of specified that I believe the issue is related because it only started happening yesterday, we haven’t updated in quite some time.

[buildthomas]

@ScriptOn

I don’t know if this is considered RobloxCritical

Here’s a reference FYI:

How to post a Bug Report

Reports without the following information will NOT be investigated Replies to bug reports must also follow these guidelines where possible. This means “Me too!” replies are not acceptable. Basics Your bug report must have: An accurate title - Engineers should know what the bug is before opening the thread. Be specific! A detailed description - Explain what you expect, and what happens instead. Where it happens - Include links if it happens with specific places / us…

Not applicable here unfortunately, has to be a crash or loss of data or major exploit

[Polymorphic]

Yeah, I’ve noticed physic constraints have stopped behaving as they used to. Rope constraints for me are weird now.

[zeuxcg]

We enabled a change that could result in something like this on Thursday. The change has been disabled a few minutes ago; @ScriptOn, can you confirm the current status (whether the problem has been fixed)?

[ScriptOn (Genya)]

Fixed, thanks! What was it?

[zeuxcg]

An attempt to switch to a correct inertia tensor for asymmetric objects; the new behavior doesn’t make sense so it’s likely that there’s a bug in some case we haven’t tested sufficiently.