Dear Justus.
This is SS6PU developer.
The update version of SS6Player for Unity (SS6PU) is released.
https://github.com/SpriteStudio/SS6PlayerForUnity
- Ver.2.1.21 : branch "develop" / "sampledevelop"
- Ver.2.2.0 : branch "develop_v2_2_0"
Both versions have largely fixed the bugs you reported, but with the following differences.
So, please consider which version you would like to update to, taking into account the current state of your project development.
When data imported in "Unity-Native" mode is placed in a hierarchy, the "Setup" animation status will be displayed if no AnimationClips are attached.
However, if the animation is changed during preview playback from "Animation" window, texture of the "Mesh" part may be lost, but textures will be restored when another animation-part is selected or when the Unity-Editor calls (MonoBehaviour's) "LateUpdate" function.
In addition, AnimationClip data and class implementations are compatible with "SS6PU Ver. 2.1.x".
When data imported in "Unity-Native" mode is placed in hierarchy, shows "animation 0 frame 0" even if no AnimationClips are attached.
Basically, I think to be your desired behavior.
However, since AnimationClip data and class implementation of "Unity-Native" mode are not compatible with the past "SS6PU Ver. 2.1.x", re-importing data is required.
("Ver. 2.2.0" is not able to correctly-play "Unity-Native" data of "Ver. 2.1.x".)
We would be happy to assist you in your development.
Best Regards,