Ok, that’s odd, so we go for software faults …
If you happen to have a USB OTG adapter, you could connect a USB mouse (and a keyboard, but that’s not so important) with the phone and navigate it this way.
What exactly does it say in Settings - About phone - Build number?
And as crazy as it sounds … Please have a look whether your WiFi is set to stay active in sleep mode. If not, enable this and see if that somehow solves this.