Why Does My Phone Hang For a while when I Simply Lock Then Try to unlock it? 0

[Android Central Question]

I Recently Bought New Phone Meizu M6 M711H! IT Works Fine But Day Ago I Installed A Theme Then Deleted It Because After Installing That When I Simply Turned Off My Screen After Couple Of Minutes I Tried To Unlock my phone It Stucked! It wasn't Working Then After 10 Seconds Approximately Screen Turned On And I Was Able To Unlock It!
It was Happening After Every Lock/unlock! So I reset my phone to its factory settings But Instead Of Hard Reset I'm Facing Same Issue!
This Is The Third Day Of My Phone But I Don't Know Why It Is Happening! I have 2GB Ram!
So Can Anyone Please Please Please Help Me? I Will Be Very very Thankful To You

 

[B. Diddy]

Welcome to Android Central! Where did you install this theme from? The Play Store, or from somewhere else?

How did you do the factory reset? Try doing it from Recovery Mode: https://www.hardreset.info/devices/meizu/meizu-m6-note/recovery-mode/