When upgrading from budgie-desktop 10.7.2-5 to 10.7.2-6, the package mutter43 must be replaced with magpie-wm, which currently depends on mutter. As mutter43 conflicts with mutter, manual intervention is required to complete the upgrade.
First remove mutter43, then immediately perform the upgrade. Do not relog or reboot between these steps.
pacman -Rdd mutter43