Samir i have noticed this bug as well before i wiped my OS, though in my case i use an app called windhawk. that was causing windows to get confused when an app opened (windhawk takes some time) and re-apply its own theme just before windhawk did. nowadays my win install is debloated and forced dark theme anyway. though on my gtbook it is noticeable after rebooting
SideNote:
Oh, and Im excited for the new release more than i was before now, i switched over to vscode (using code runner for now until a debugger was released). though im a bit sad about studio leaving the scene