Scene not saving, losing .fbx files in scene

[JegoMx]

I've been playing around with the editor a few days now. However, one issue I've noticed is how often scene data gets completely lost inbetween opening/closing the project, no matter if I have saved or not. I will put in an object in the scene, save the scene, build, run, test, etc... All is good. I close the project to work on it after lunch. Upon re-opening the project, all those scene changes are gone!

To be clear, I'm using the File -> Save Project (Ctrl + S) functionality. Could some verify whether they encounter the same issues? Or could someone point out what I did wrong in order to fix this problem? Thanks in advance.

Update: Only ever happens to .fbx files directly placed into a scene, .glb and .babylon extensions are working fine.