Oppo
Auto-Arrange App Icons on the Home Screen auf Oppo
Icon autofill on Oppo phones keeps every app shortcut in a fixed reading order. New apps land in the next free slot, sorted left to right and line by line. While this is active, you cannot drag an icon to an empty spot of your choice. You can only move it to another position within that same ordered sequence.
This behavior is a setting inside the home screen management, not a bug. It exists to keep grids tidy after installs or uninstalls, but it removes manual control over layout.
Where to find the setting
Open Settings, then tap Home screen, Lock screen & Always-On Display, then find the toggle for Icon autofill. Switching it off lets you place icons anywhere, including empty gaps left behind by deleted apps. Switching it back on re-sorts everything into rows again.
If you only want a specific icon to stay put while keeping the rest tidy, autofill will not help. It applies to the whole home screen layout, not individual apps.