@4ian
I can confirm the flicker when you change the scene and load an external layout. It doesn’t seems to appear when you load the scene initially but when you change the scene.
it maybe got something to do with the new engine.
I tried this project of mine:
The one you can play on the website was exported from GD4. When you go to the hangar and select fitting and hull it is loading the content from external layout and I don’t experience any flicker.
If you download the source and load it in to the current version of GD5 and run preview the flicker does appear when you go to the hangar and change between fitting and hull back and forth.