Bad Root - Massive Instability

[Breadohs]

Evening / Morning, all...

I wanted to ask a question about my Note 4, N910F, on Vodafone.

My situation is, a bad root forced me to flash back to original factory ROM's, but
as of right now, the phone is suffering from massive hanging, random re-boots and overall unresponsiveness
after around 20 minutes, until the battery is taken out and the device is powered back on.

I'm looking for a fix that will hopefully not mean me shelling out for a brand new motherboard for
the phone. The Knox fuse has been tripped, so I'm somewhat apprehensive about sending it over to Samsung
only to be without a phone for a week, and then politely told to **** off.

Does anyone have any clue as to what might be causing the issues?
And has anyone had any experiences with having Knox-tagged phones replaced or repaired under Vodafone?

Thanks for reading,

Bread

BTW. System Specs -

Model Number - N910F
Android Version - 5.1.1
Build Number - LMY47X.N910FXXS1CPC6
Knox 2.4.1

 

[Jfalls63]

Where did you get the stock firmware? Sammobile?

http://www.sammobile.com/firmwares/database/SM-N910F/

Could be as simple as flashing the firmware again.

 

[Shazam52]

Can you recall the steps you took in attempting to root the device? Maybe you missed a step?