Please Help identifying: screen issue vs something else?

Hello! Thanks in advance!

I need help from someone who has dealt with the following before:

iPhone 6 Plus. Works fine, however a few times per day the screen will NOT turn on.

The backlight will come on instead. After that I would (don't laugh) knock on the display a few times with my knuckles and the screen comes ON but pale (full of white lines) and the touch surface is not responsive at this point. Every time after that I hit the power button twice and the phone comes back to normal until the next occasion.

Note: the phone itself seems to WORK when the screen is off. I can take screenshots and find them in the gallery later (lock screen) OR if I unlock the phone with Touch ID and then lock it back, I can hear the "locking" sound.

I did drop my phone a few times before this started to happen.

Tried hard reset, didn't help (the problem repeats shortly afterwards)

Question to you folks, is this the hardware or software issue? Will replacing the screen fix this problem?