he @Leonidas,
absolutly. this is why i was mentioning the preloader. it does load() the textures i need. i cycle through all material slots of all materials which will be shown in the scene upfront find them in registry and then i .load() them. after the reset i use the array i have to unload them. i also tryed to tag them and use this.app.assets.findByTag() to rule out removing any texture i don’t want to be unloaded (like some custom opacity maps).
found this thread meanwhile. that guy mentions a similar thing when textures are shared between his scenes. it may be possible the textures that fail are used in the scene before i reset it.