Kerbal Space Program

How to reproduce: take a fairing, attach either a heatshield with enabled staging or some decoupler with a part beneath it to the fairing. It can be the main fairing node or interstage node, doesn't matter. Then close the fairing on a heatshield or a part. Launch craft, then try to decouple. Parts that supposed to be decoupled stay attached as if they are still on the same vessel, but they are not. You can switch to them as shown in the second video, but they behave as if they are still attached. When you enable time warp, physics completely fail and decoupled parts just fall to the ground and explode.
Video #1: https://youtu.be/7JU48QKtN8Q
Video #2: https://youtu.be/wvLroh3tsSc

And apparently it doesn't work only in one direction. Only if you try to decouple something from the fairing. If you decoupling the fairing itself, it works as intended.
Video #3: https://youtu.be/cuT0zviOW2M

Also, rcs doesn't work until you leave the render range of the fairing.

Video #4: https://youtu.be/PlzA5X7PfmQ

I think it has something to do with the root part of the vessel. If the fairing stays with the root part of the vessel, nothing is decoupling from it. If the fairing decouples from the root of the vessel (i.e. interstage of the rocket on the first stage with the root part on the second stage), then it's fine. See the attached video for demonstration.

Video #5: https://youtu.be/SgZHApejBs4