Vehicles stacked on top of another vehicle seemingly stuck in on ground state

[Mathmagician]

Game Version​

2026.10.19.5638

Operating System​

Linux Mint 22.2

What Happened​

I launched a rocket with insufficient thrust to take off while full of fuel, then detached the capsule on top. The rocket struggled to move upwards, then after burnout the rocket fell down but left the capsule hanging in the air. After manually triggering an RCS pulse, the capsule started falling towards the ground.

What Was Expected​

The rocket would reach a significant speed after burning enough fuel to reach a TWR > 1 (and likely also fall over due to lack of control). If the capsule is left attached, this expected behaviour occurs.

Reproduction Steps​

1. Use the vehicle from the attached zip file
2. Press Z to enable the engine, then stage twice
3. After a while, the rocket should start moving upwards very slowly once its TWR exceeds 1
4. When the rocket burns out, it should fall back to the ground leaving the capsule floating
5. Pulsing the RCS should make it fall back to the ground

Reproduction Rate​

Has occurred 2/2 times in my testing

Additional Info​

Attachments: a screenshot of the floating capsule after the rocket burns out and falls to the ground, and a zip of a vehicle that can replicate the bug.