Android Interface too easy to circumvent

I'm not totally sure how this is happening, but the Android version of the software is apparently entirely too easy to circumvent.

I have three Android devices with Bitdefender installed, it was installed in order to prevent children from accessing the Play Store and to deny access to messaging apps. As of recently these protections have failed, a 10 y/o who is hardly tech savvy is circumventing the controls in order to gain access to apps from which he is locked out of and we can't figure out how. To our knowledge, he doesn't know the PIN which is required to unlock apps and to activate/deactivate the app lock.

In a couple instances, the app has been uninstalled entirely from the phone, which is hard to fathom given that the Play Store is locked and seems to only have a deactivate button in Google Play. To counter that, I tried activating app lock for the Settings app, which doesn't seem to have helped. Today, however, he had somehow got into the app lock settings and disabled the lock on a particular app.

I cannot figure out he is doing this, but Bitdefender is not providing strict enough protections and is allowing access to apps that are supposed to be protected.

What can be done about this?