Stuck in a boot loop after opening an app.

If a wipe doesn't fix it then the problem is in the system software, which your system partition check seems to confirm. If you've been installing apps from less than reliable sites it's possible that one of them included a rootkit malware (i.e. malware that exploits the same security weaknesses used to root phones in order to install itself as a system app, making it resistant to a factory reset).

My advice would be to try to reflash the phone with a new set of official software. However, the tools and procedures for that depend on the manufacturer, and I have no experience of Lenovo devices, so can't tell you how to do this.