Optimizing app 1 of 1 on Android starting after GooglePlay update

I have a Lenovo Tab3 8 Tablet that had been working fine until about five-six months ago. Then I got this Optimizing app 1 of 1 message one day, when I had to restart the tablet, which basically made the device useless. I have been trying to fix it ever since, but every time I do the emmc factory reset from the boot menu it lasts only until the next reboot. That is, however, only when I update the device over GooglePlay before rebooting. If I reboot without updating, it doesn't show the Optimizing app message, and I can log in my profile, but then the first time I have to use GooglePlay to add a new app or autoupdate the system, the same issue reappears and I have to do the reset all over again. This seems to be due to some faulty GooglePlay update routine involving preinstalled apps. It's extremely frustrating. Anybody with the same problem on this device, or similar model/OS version? Anything is welcome! Here's all the system info I managed to get from the sys menu of the tablet: Model number: Lenovo TB3-850M Android version: 6.0 Kernel version: 3.18.19 Build number: TB3-850M_S100036_171214_ROW Software version: TB3-850M_160509