Question [Q] Touch screen stops responding must reboot to fix

Recently two n5 we have in the family started doing the same thing,
touch screen is not responsive (buttons do work) and the device must be
rebooted holding the power button to get it working again.
Quite annoying since it happens couple times every day.
Searched around but didn't find any reports.
Both phones stock, rooted, gravity box and touch control installed.

Any ideas?
Thanks