My wife's ip6 is currently having this problem.
Frozen screen, crazy screen.
Same with u, only power button, home works if it is in stupid state.

Its iphone6 128gb from umobile.

From the net, it seems other fellow experiencing same problem with theirs. Macrumor forum. It shows how to overcome the prob also.

Rm1.7k for screen is a lot. My trusty running 4yo XperiaZ cost that much when new.