@Seven.of.nine This seems to be a common.problem also -and not at all surprising- with Android devices.
Not all data is erased after sw deinstallation. Some stuff remains which does or does not interfere with the system. There is Mashka for ckeaning up SF on.openrepos but it doesn’t help with all sw debris and certainly not with Android stuff.
Factory resets are an act of purification that might brighten up your soul as well as your device. 