OnePlus is data mining the shit out of their phones now.
OnePlus no longer provides the tools to fully restore the device in case of a software brick. So backup all your files if you plan to factory reset.
The storage loss is probably an auto downloaded software rom update that did not delete after upgrading it. Poor programming from OnePlus. They don't really back their devices anymore.
CCleaner has been hacked multiple times over the years, putting your data at risk. Be careful.
I would not recommend using a Android device, stuck on A11, that has you personal banking, cash apps, email, password managers. Be very careful running any android device that does not have up to date security software. All those free apps on the play store prey on deficiencies in the open platform.
Basically get a new phone. If you prefer OnePlus, at least get the newer models with at least A12 and a 2023 security package. In reality purchase from another manufacturer.
Yea Its time to upgrade then..not gonna fuck with OnePlus again.