Vehicle Instance is broken (nan error)

[tobiblender]

Godot version:
3.2 stable
OS/device including version:
Win8
Issue description:
i instance a vehicle (tscn) several times per gdscipt (preload) in a for-loop.
the first instance is allways somehow broken - it gets transform-vectors with "-1.#QO" throws an error.
i found out about the cause via the debugger > breakpoints feature

the console puts Error NAN
E 0:00:00.712 instance_set_transform: Condition "Math::is_nan(v.x)" is true.
<C++-Quellcode>servers/visual/visual_server_scene.cpp:601 @ instance_set_transform()

Steps to reproduce:

• open the project
• open the scene vehicle_instance_bug.tscn
• press F5
• the output throws the NAN Error

as i said - i investigated via debugger and found out that the error is allways from the first instance
the following instances are fine.

Minimal reproduction project:
Vehicle_instance_bug_1.zip

[tobiblender]

PS: this does not happen in 3.1.2 (with same project)

[groud]

Please provide a minimal reproduction project.

[tobiblender]

Hi again :)
okay i made a mini-project to show it off.

[matkoniecz]

It appeared to me after clean Godot install, downloading Truck Town project and selecting Tow Truck as an option. (also happens with the middle option)

[Demindiro]

I suspect it is a thread synchronization issue, since changing seemingly unrelated things "fixes" it (e.g. if the VehicleBody node is not in a separate scene the bug won't occur, if it is it does) and it doesn't happen consistently. In either case, I tried to narrow it down as much as possible.

vehicle_is_nan.zip

When spamming the "Spawn" button, the issue does occur eventually.

[qarmin]

I found that m_suspensionLength variable was uninitialised and sometime had Nan value.
From my tests initializing it with zero fixes problem.

[pouleyKetchoupp]

Junior job hint:
Based on #44125 (comment), this issue can be fixed separately from #44630/#44125 by just setting the default value to m_suspensionLength.