Back Button Not working in Android Galaxy Redmi Lenovo Moto X

Back Button Home Screen and Recent Apps buttons were not working on Android Mobiles Motorola Moto G Moto X Style Play Moto Z Moto E Samsung Galaxy S8 S7 S6 S5 J7 J5 J3 Note Tab Redmi Note 3 4 Mi4 Lenovo K3 Note HTC one Desire Wildfire LG G4 G5 Sony Xperia One Plus

Cause
After OS upgrade, security patch update or kept your phone in back pocket.
Initially you may face Ghost touch problem, after some times your back button may stop working permanently.

Back Button Not working

1) Wipe cache partition and restart the mobile
If this didn’t solve the problem

2)For Samsung Galaxy Mobile dial the USSD Code – *#2663#
and click the TSP FW Update – > restart the mobile
OR
Go to settings > my device > display > touch key light duration, set to 1.5 seconds.
If this didn’t solve the problem

3) Try Factory Data Reset (FDR) with no auto restore
Go to Settings -> Backup & Reset –> (disable) Automatic Restore
Now go to Settings -> Backup & Reset -> Factory Data Reset

If FDR didn’t solve the problem, then there may be some hardware issue.
You have to contact the Customer care.

Temporary solution

If your mobile is not in warranty, then you can try any one of the following solution.

Change your display size to Large (Working in Motorola Moto X Style)
Go to Settings -> Display -> Display Size -> Set the Large Size

Or

You can use custom back button APP.